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Tamilnadu Samacheer Kalvi 12th Bio Botany Solutions Chapter 7 Ecosystem

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Samacheer Kalvi 12th Bio Botany Ecosystem Text Book Back Questions and Answers

Question 1.
Which of the following is not a abiotic component of the ecosystem?
(a) Bacteria
(b) Humus
(c) Organic compounds
(d) Inorganic compounds
Answer:
(b) Humus

Question 2.
Which of the following is / are not a natural ecosystem?
(a) Forest ecosystem
(b) Rice field
(c) Grassland ecosystem
(d) Desert ecosystem Pond is a type
Answer:
(b) Rice field

Question 3.
Pond is a type of __________
(a) Forest ecosystem
(b) grassland ecosystem
(c) marine ecosystem
(d) fresh water ecosystem Pond ecosystem
Answer:
(d) fresh water ecosystem Pond ecosystem

Question 4.
Pond ecosystem is __________
(a) not self sufficient and self regulating
(b) partially self sufficient and self regulating
(c) self sufficient and not self regulating
(d) self sufficient and self regulating
Answer:
(d) self sufficient and self regulating

Question 5.
Profundal zone is predominated by heterotrophs in a pond ecosystem, because of __________
(a) with effective light penetration
(b) no effective light penetration
(c) complete absence of light
(d) a and b
Answer:
(d) a and b

Question 6.
Solar energy used by green plants for photosynthesis is only __________
(a) 2 -8%
(b) 2-10%
(c) 3-10%
(d) 2-9%
Answer:
(b) 2-10%

Question 7.
Which of the following ecosystem has the highest primary productivity?
(a) Pond ecosystem
(b) Lake ecosystem
(c) Grassland ecosystem
(d) Forest ecosystem
Answer:
(c) Grassland ecosystem

Question 8.
Ecosystem consists of __________
(a) decomposers
(b) producers
(c) consumers
(d) all of the above
Answer:
(d) all of the above

Question 9.
Which one is in descending order of a food chain?
(a) Producers → Secondary consumers → Primary consumers → Tertiary consumers
(b) Tertiary consumers → Primary consumers → Secondary consumers → Producers
(c) Tertiary consumers → Secondary consumers → Primary consumers → Producers
(d) Tertiary consumers → Producers → Primary consumers → Secondary consumers Significance of food web is / are
Answer:
(c) Tertiary consumers → Secondary consumers → Primary consumers → Producers

Question 10.
Significance of food web is / are __________
(a) it does not maintain stability in nature
(b) it shows patterns of energy transfer
(c) it explains species interaction
(d) b and c
Answer:
(d) b and c

Question 11.
The following diagram represents __________

(a) pyramid of number in a grassland ecosystem
(b) pyramid of number in a pond ecosystem
(c) pyramid of number in a forest ecosystem
(d) pyramid of biomass in a pond ecosystem
Answer:
(c) pyramid of number in a forest ecosystem

Question 12.
Which of the following is / are not the mechanism of decomposition?
(a) Eluviation
(b) Catabolism
(c) Anabolism
(d) Fragmentation
Answer:
(c) Anabolism

Question 13.
Which of the following is not a sedimentary cycle?
(a) Nitrogen cycle
(b) Phosphorous cycle
(c) Sulphur cycle
(d) Calcium cycle
Answer:
(a) Nitrogen cycle

Question 14.
Which of the following are not regulating services of ecosystem services?
(i) Genetic resources
(ii) Recreation and aesthetic values
(iii) Invasion resistance
(iv) Climatic regulation
(a) i and iii
(b) ii and iv
(c) i and ii
(d) i and iv
Answer:
(c) i and ii

Question 15.
Productivity of profundal zone will be low. Why?
Answer:
The producers of the pond ecosystem depends on phytoplankton through photosynthesis. Profundal zone lies below the limnetic zone with no effective light penetration, hence productivity rate is very low.

Question 16.
Discuss the gross primary productivity is more efficient than net primary productivity.
Answer:
Gross primary productivity:

1. It refers to the total amount of food energy or organic matter produced in an ecosystem by autotrophs.
2. GPP = NPP + Respiration

Net primary productivity:

1. It refers to the amount of energy that remain in autotrophs after respiration loss.
2. NPP = GPP – Respiration

Question 17.
Pyramid of energy is always upright. Give reasons.
Answer:
The energy pyramid represents a successive energy flow at each trophic level in an ecosystem. There is a gradual decrease in energy transfer at successive tropic levels from producers to higher levels, hence the pyramid of energy is always upright.

Question 18.
What will happen if all producers are removed from ecosystem?
Answer:
Producers are the autotrophs which occupy the first tropic level in an ecosystem. The energy produced by them is utilized by the herbivores and then by carnivores, thereby maintaining the stability of ecosystem. If producers are removed from an ecosystem, it would lead to starvation and death of herbivores and subsequently the carnivores, thus terminating the entire food web.

Question 19.
Construct the food chain with the following data.
Hawk, plants, frog, snake, grasshopper.
Answer:
Plants → Grasshopper → Frog → Snake → Hawk

Question 20.
Name of the food chain which is generally present in all type of ecosystem. Explain and write their significance.
Answer:
Detritus food chain is common in all type of ecosystem. In detritus food chain, the dead remains of plant and animals or their excreta are broken down by detrivores and the organic and inorganic substances are returned back to environment. Thus maintaining die company of various biogeochemical cycles. Also Microbes growing on detritus makes the soil nutritious for consumers.

Question 21.
Shape of pyramid in a particular ecosystem is always different in shape. Explain with example.
Answer:
In a forest ecosystem the pyramid of number is spindle in shape, it is because the base (T₁) of the pyramid occupies large sized trees (Producer) which are lesser in number. Herbivores (T₂) (Fruit eating birds, elephant and deer) occupying second trophic level, are more in number than the producers. In final trophic level (T₄), .tertiary consumers (lion) are lesser in number than the secondary consumer (T₃) (fox and snake).

Question 22.
Generally human activities are against to the ecosystem, where as you a student how will you help to protect ecosystem?
Answer:

1. Buying and using only ecoffiendly products and recycle them.
2. Growing more trees.
3. Choosing sustained farm products (vegetables, fruits and greens, etc.)
4. Reducing the use of natural resources.
5. Recycling the waste and reduce the amount of waste you produce.
6. Reducing consumption of water and electricity.
7. Reducing or eliminating the use of house-hold chemicals and pesticides.
8. Maintaining your cars and vehicles properly to reduce carbon emission.
9. Creating awareness and educate about ecosystem protection among your friends and family members and ask them to find out solution to minimise this problem.

Question 23.
Generally in summer the forest are affected by natural fire. Over a period of time it recovers itself by the process of successions. Find out the types of succession and explain. Secondary succession.
Answer:
The development of a plant community in an area where an already developed community has been destroyed by natural causes is known as secondary succession. This type of succession takes less time to occur.

Question 24.
Draw a pyramid from following details and explain in brief.
Answer:
Quantities of organisms are given-Hawks-50, plants-1000, rabbit and mouse-250 +250, pythons and lizard – 100 + 50 respectively

T₄ (50) T₃ (100) T₂ (550) T₁ (1000)
The pyramid produced is an upright pyramid of numbers where there is a gradual decrease in number of organisms at each trophic level from T₁ to T₄. This is an example for grassland ecosystem.

Question 25.
Various stages of succession are given bellow. From that rearrange them accordingly. Find out the type of succession and explain in detail.
Answer:
Reed-swamp stage, phytoplankton stage, shrub stage, submerged plant stage, forest stage, submergedfree floating stage and marsh medow stage.

(1) Phytoplankton stage – It is the first stage of succession consisting of the pioneer community like blue green algae, green algae, diatoms, bacteria, etc., The colonization of these organisms enrich the amount of organic matter and nutrients of pond due to their life activities and death. This favors the development of the next serai stages.

(2) Submerged plant stage – As the result of death and decomposition of planktons, silt brought from land by rain water, lead to a loose mud formation at the bottom of the pond. Hence, the rooted submerged hydrophytes begin to appear on the new substratum.
Example: Vallisneria and Hydrilla etc. The death and decay of these plants will build up the substratum of pond to become shallow.

(3) Submerged free floating stage – During this stage, the depth of the pond will become almost 2-5 feet Hence, the rooted hydrophytic plants and with floating large leaves start colonising the pond.
Example: Rooted floating plants like Nelumbo, Nymphaea and some free floating species like Azolla, and Pistia are also present in this stage. By death and decomposition of these plants, further the pond becomes more shallow.

(4) Reed-swamp stage – It is also called an amphibious stage. During this stage, rooted floating plants are replaced by plants which can live successfully in aquatic as well as aerial environment.
Example: Typha, Phragmites, Sagittaria and Scirpus etc. At the end of this stage, water level is very much reduced, making it unsuitable for the continuous growth of amphibious plants.

(5) Marsh meadow stage – When the pond becomes swallowed due to decreasing water level, species of Cyperaceae and Poaceae colonise the area. They form a mat-like vegetation with the help of their much branched root system. This leads to an absorption and loss of large quantity of water. At the end of this stage, the soil becomes dry and the marshy vegetation disappears gradually and leads to shurb stage.

(6) Shrub stage – Here areas are invaded by terrestrial plants like shrubs (Salix and Comus) and trees (Populus and Alnus). These plants absorb large quantity of water and make the habitat dry. Further, the accumulation of humus with a rich flora of microorganisms produce minerals in the soil, ultimately favouring the arrival of new tree species in the area.

(7) Forest stage – It is the climax community of hydrosere. A variety of trees invade the area and develop any one of the diverse type of vegetation.
Example.Temperate mixed forest (Ulmus,Acer and Quercus), Tropical rain forest (Artocaipus and Cinnamomum ) and Tropical deciduous forest (Bamboo and Tectona).

Samacheer Kalvi 12th Bio Botany Ecosystem Additional Questions and Answers

1 – Mark Question

Question 1.
Ecosystem is the structural and functional unit of ecology. This statement was given by ___________
(a) Tansley
(b) Odum
(c) Charles Elton
(d) Edwin
Answer:
(b) Odum

Question 2.
Identify the incorrect option among the following component sequence.
(a) air, water, sunlight and temperature
(b) latitude, altitude, direction of mountain and aptitude
(c) soil air, pH of soil, saltwater and soil moisture
(d) carbohydrate, protein, lipids and humic substances
Answer:
(b) latitude, altitude, direction of mountain and aptitude

Question 3.
Pick out the edaphic factor among the following.
(a) Rainfall
(b) Temperature
(c) Soil pH
(d) Latitude
Answer:
(c) Soil pH

Question 4.

Answer:
a -ii, b – iii, c – iv, d-i

Question 5.
Which is not a macro consumer?
(a) Herbivore
(b) Carnivore
(c) Ominivore
(d) Decomposer
Answer:
(d) Decomposer

Question 6.
Photosynthetically Active Radiation ranges between the wavelength of.
(a) 400 – 600 nm
(b) 600 – 700 nm
(c) 400 – 500 nm
(d) 400 – 700 nm
Answer:
(d) 400 – 700 nm

Question 7.
Who coined the term Ecosystem?
Answer:
A.G. Tansley

Question 8.
Identify the incorrect statement.
(a) Carbon stored in oil is referred as Grey carbon
(b) Carbon stored in atmosphere is referred as Blue carbon
(c) Carbon stored in industrialized forests is referred as Green carbon
(d) Carbon emitted from gas, died engine is referred as Black carbon
Answer:
(c) Carbon stored in industrialized forests is referred as Green carbon

Question 9.
Which group of organism occupies the third tropic level in an ecosystem?
(a) Primary consumers
(b) Secondary consumers
(c) Secondary carnivores
(d) Omnivores
Answer:
(b) Secondary consumers

Question 10.
Which is irrelevant to the first law of thermodynamics?
(a) Energy can be transmitted from one system to other in many forms.
(b) Energy transformation results in reduction of free energy.
(c) Energy can neither be created nor destroyed.
(d) Energy in the universe is constant.
Answer:
(b) Energy transformation results in reduction of free energy.

Question 11.
If 1200 Joules of solar energy is trapped by producers, how much of Joules of energy does the organism in the third trophic level will receive?
(a) 120 Joules
(b) 12 Joules
(c) 1.2 Joules
(d) 0.12 Joules
Answer:
(c) 1.2 Joules

Question 12.
Which of the following food chain is in improper sequence?
(a) Plants → snake → rabbit → lizard → eagle
(b) Plants → grasshopper → lizard → snake → hawk
(c) Plants → lizard → rabbit → snake → eagle
(d) Plants → rabbit → lizard → hawk → eagle
Answer:
(b) Plants → grasshopper → lizard → snake → hawk

Question 13.
Which one of the following is not a functional unit of an ecosystem?
(a) Productivity
(b) Conductivity
(c) Energy flow
(d) Decomposition
Answer:
(b) Conductivity

Question 14.
The upright pyramid is not a feature of. __________
(a) Pond ecosystem
(b) Grassland ecosystem
(c) Forest ecosystem
(d) Terminal ecosystem
Answer:
(a) Pond ecosystem

Question 15.
The type of ecosystem with maximum net primary productivity is __________
(a) Desert ecosystem
(b) Deciduous forest ecosystem
(c) Tropical rain forest ecosystem
(d) Grassland ecosystem
Answer:
(c) Tropical rain forest ecosystem

Question 16.
Pyramid of numbers with broad base indicates __________
(a) High population of old individuals
(b) Low population of young individuals
(c) High population of young individuals
(d) Low population of old individuals
Answer:
(b) Low population of young individuals

Question 17.
Spindle shaped pyramid is a character of __________
(a) Pond ecosystem
(b) Grassland ecosystem
(c) Parasite ecosystem
(d) Forest ecosystem
Answer:
(d) Forest ecosystem

Question 18.
Read the statement and select the correct terminology for the same:
“Carrying away of inorganic compounds of soil by water”.
(a) Eluviation
(b) Fragmentation
(c) Humification
(d) Mineralisation
Answer:
(a) Eluviation

Question 19.
Complete the food chain by filling the link X:
Paddy → Grassopper → Frog → X → Hawk
(a) King cobra
(b) Gorilla
(c) Rabbit
(d) Tasmanial wolf
Answer:
(a) King cobra

Question 20.
Which of the following is abundant in rock deposits and guano?
(a) Nitrogen
(b) Phosphorous
(c) Oxygen
(d) Calcium
Answer:
(b) Phosphorous

Question 21.
The bottom most zone of a pond is termed as
(a) Limnetic zone
(b) Littoral zone
(c) Benthic zone
(d) Profundal zone
Answer:
(c) Benthic zone

Question 22.
Observe the figures and select the correct type of pyramid of numbers

Answer:
(a) (A) Grassland ecosystem (B) Forest Echosystem (c) Parasite ecosystem

Question 23.
Lotic ecosystem refers to ___________
(a) Open water ecosystem
(b)Running water ecosystem
(c) Standing water
(d) Ocean water ecosystem
Answer:
(b)Running water ecosystem

Question 24.
Identify the correct sequence of various zones from surface to depth in a pond ecosystem.
(a) Profundal, limnetic, littoral and benthic
(b) Benthic, littoral, profundal and limnetic
(c) Limnetic, profundal, littoral and benthic
(d) Littoral, limnetic, profundal and benthic
Answer:
(d) Littoral, limnetic, profundal and benthic

Question 25.
Which type of ecosystem service does the genetic resources comes under?
(a) Provisioning services
(b) Supporting services
(c) Regulating services
(d) Cultural services
Answer:
(a) Provisioning services

Question 26.
Assertion (A): Pyramid of energy is upright.
Reason (R): During the energy transfer at successive trophic levels from producers there will be a gradual decrease
(a) Both A and R are wrong
(b) A is right R is wrong
(c) R explains A
(d) A is right R is not the correct explanation for A
Answer:
(c) R explains A

Question 27.
Assertion (A): In forest ecosystem, the pyramid of number is spindle shaped.
Reason (R): Tropical level (T₁) of the pyramid occupies large trees which are maxium in number
(a) Both A and R are wrong
(b) A is right R is wrong
(c) R explains A
(d) A is right R is not the correct explanation for A
Answer:
(b) A is right R is wrong

Question 28.
Species that indicate the health of the ecosystem are called as __________
Answer:
Flagship species

Question 29.
Succession initiating on a sand referred as
(a) Hydrosere
(b) Psammosere
(c) Halosere
(d) Lithosere
Answer:
(b) Psammosere

Question 30.
Match the column I with column II

Answer:
(a) a – iii, b – iv, c – i, d – ii

Question 31.
Statement (I): Allogenic succession occurs as a result of abiotic factors.
Statement (II): Autogenic succession occurs as result of biotic factors.
(a) Statement I is correct; Statement II is incorrect.
(b) Statement I is incorrect; Statement II is correct.
(c) Both Statements I and II are correct.
(d) Both Statements I and II are incorrect.
Answer:
(c) Both Statements I and II are correct.

Question 32.
Statement (I): The first invaded plants in a barren area are called as pioneers.
Statement (II): Marsh meadow stage of hydrosere succession is also called as amphibious stage.
(a) Statement I is correct; Statement II is incorrect.
(b) Statement I is incorrect; Statement II is correct.
(c) Both Statements I and II are correct.
(d) Both Statements I and II are incorrect.
Answer:
(a) Statement I is correct; Statement II is incorrect.

Question 33.
_______ is the climax community of hydrosere.
(a) Reed swamp stage
(b) Marsh medow stage
(c) Shrub stage
(d) Forest stage
Answer:
(d) Forest stage

2-Mark Questions 

Question 1.
According to A.G. Tansley, what is an ecosystem?
Answer:
A.G. Tansley (1935), who defined ecosystem as ‘the system resulting from the integration of all the living and non-living factors of the environment.

Question 2.
Mention any two climatic factors and edaphic factors of an ecosystem.
Answer:

1. Climatic factors: Light and Air.
2. Edaphic factors: Soilwaer and pH of soil.

Question 3.
Define ‘Standing state’ with regard to ecosystem.
Answer:
The total inorganic substances present in any ecosystem at a given time is called standing quality (or) standing state.

Question 4.
What are biotic components?
Answer:
Biotic (living) components includes all living organisms like plants, animals, fungi and bacteria. They form the trophic structures of any ecosystem.

Question 5.
Name the macro consumers and micro consumers.
Answer:

1. Macro consumers are herbivores, carnivores and omnivores.
2. Micro consumers are decomposers.

Question 6.
How will you define decomposers?
Answer:
Decomposers are organisms that decompose the dead plants and animals to release organic and inorganic nutrients into the environment which are again reused by plants.
Example: Bacteria, Actinomycetes and Fungi.

Question 7.
What is standing crop?
Answer:
The amount of living materials present in a population at any given time is known as standing crop, which may be expressed in terms of number or biomass per unit area.

Question 8.
What do you mean by PAR? Mention its significance.
Answer:
The amount of light available for photosynthesis of plants is called Photosynthetically Active Radiation (PAR) which is between the range of 400-700 mm wave length.

Question 9.
Pointout the factors that affects the photosynthetically active radiation.
Answer:
PAR is not always constant because of clouds, tree shades, air, dust particles, seasons, latitudes and length of the daylight availability.

Question 10.
Define Grey carbon and Black carbon.
Answer:
Grey carbon – carbon stored in fossil fuel (coal, oil and biogas deposits in the lithosphere). Black carbon – carbon emitted from gas, diesel engine and coal fired power plants.

Question 11.
What is meant by productivity of an ecosystem?
Answer:
The rate of biomass production per unit area in a unit time is called productivity. It can be expressed in terms of gm /m²/year or Kcal/m²/ year.

Question 12.
How Net Primary Productivity can be derived?
Answer:
Net Primary Productivity (NPP) is derived by the difference between Gross primary productivity (GPP) and respiration.
NPP = GPP – Respiration

Question 13.
Expand GPP and define it.
Answer:
Gross Primary Productivity (GPP) is the total amount of food energy or organic matter or biomass produced in an ecosystem by autotrophs through the process of photosynthesis is called gross primary productivity.

Question 14.
Write the name of four important aspects of ecosystem.
Answer:

1. Productivity
2. Energy flow
3. Decomposition
4. Nutrient cycling

Question 15.
State the role of herbivores and microconsumers in a terrestrial ecosystem.
Answer:

1. Herbivores acts as primary consumers of producers (Plants).
2. Microconsumers decomposes the dead remains and excreta of plants and animals.

Question 16.
Name the category of organisms that occupy the first tropic level (T₁) and fourth tropic level (T₄) in an ecosystem.
Answer:
Producers (autotrophs) occupy the first tropic level (T₄) whereas the fourth tropic level (T₄) is occupied by Tertiary Consumers (Secondary carnivore).

Question 17.
What is energy flow?
Answer:
The transfer of energy in an ecosystem between trophic levels can be termed as energy flow. It is the key function in an ecosystem. Energy flow is always unidirectional in an ecosystem.

Question 18.
State the first law of thermodynamics.
Answer:
First law of thermodynamics states that energy can be transmitted from one system to another in various forms. Energy cannot be destroyed or created. But it can be transformed from one form to another. As a result, the quantity of energy present in the universe is constant.

Question 19.
State the ten percent law.
Answer:
Ten percent law states that during transfer of food energy from one trophic level to other, only about 10% stored at every level and rest of them (90%) is lost in respiration, decomposition and in the form of heat.

Question 20.
Define food chain.
Answer:
The movement of energy from producers upto top carnivores is known as food chain, i.e., in any food chain, energy flows from producers to primary consumers, then from primary consumers to secondary consumers, and finally secondary consumers to tertiary consumers. Hence, it shows linear network links.

Question 21.
Name the two types of food chain.
Answer:

1. Grazing food chain
2. Detritus food chain

Question 22.
Which is the first link in a grazing food chain and a detritus food chain?
Answer:

1. The first link of grazing food chain is plants (Producers).
2. The first link of detritus food chain is dead remains and excreta of plants and animals.

Question 23.
Rearrange the components of the ecosystem and frame a food chain. Also mention the type of food chain.
Hawk, Earthworm, Animal excreta and Black bird.
Answer:
Animal excreta → Earthworm → Black bird → Hawk. It is a detritus food chain.

Question 24.
Define food web.
Answer:
The inter-locking pattern of a number of food chain form a web like arrangement called food web. It is the basic unit of an ecosystem, to maintain its stability in nature.

Question 25.
What is Eltoian pyramid?
Answer:
Eltonian pyramid or Ecological pyramid is a graphic representation of the trophic structure and function at successive trophic levels of an ecosystem.

Question 26.
Why do we obtain an inverted pyramid in a parasite ecosystem?
Answer:
The pyramid of number in a parasite ecosystem is always inverted, because it starts with a single tree. Therefore there is gradual increase in the number of organisms in successive tropic levels from producer to tertiary consumers.

Question 27.
What is pyramid of biomass?
Answer:
A graphical representation of the amount of organic material (biomass) present at each successive trophic level in an ecosystem is called pyramid of biomass.

Question 28.
Biogeochemical cycle comprises both gaseous cycle and sedimentary cycle. How they differ from one another?
Answer:

1. The components of gaseous cycle are placed in atmosphere
   E.g: Oxygen in air
2. whereas in sedimentary cycle, the components are present in/on Earth.
   E.g: Phosphorous in rocks.

Question 29.
Name the type of ecosystem that exhibits the following types of pyramid.

1. Inverted pyramid of biomass
2. Spindle shaped pyramid of number

Answer:

1. Pond ecosystem
2. Forest ecosystem.

Question 30.
Cite few examples of biomolecules that contain phosphorus.
Answer:
DNA, RNA, ATP and NADP.

Question 31.
What are Blue carbon ecosystems?
Answer:
Sea grasses and mangroves of Estuarine and coastal ecosystems are the most efficient in carbon sequestration. Hence, these ecosystems are called as “Blue carbon ecosystems”.

Question 32.
Mention the four categories of ecosystem services.
Answer:

1. Provisioning services
2. Cultural services
3. Supporting services
4. Regulating services

Question 33.
What is meant by Ecosystem resilience?
Answer:
Ecosystem is damaged by disturbances from fire, flood, predation, infection and drought, etc. removing a great amount of biomass. However, ecosystem is endowed with the ability to resist the damage and recover quickly. This ability of ecosystem is called ecosystem resilience or ecosystem robustness.

Question 34.
Ecosystem management – comment on the statement.
Answer:
Ecosystem management is a process that integrates ecological, socio economic and institutional factors into a comprehensive strategy in order to sustain and enhance the quality of the ecosystem to meet current and future needs

Question 35.
Which kind of organisms constitute the pioneer community and climax community of a Hydrosere succession?
Answer:
Phytoplanktons from the poineer community and a variety of trees makes the climaxe community of a Hydrosere

Question 36.
Define plant succession.
Answer:
Successive replacement of one type of plant community by the other of the same area/ place is known as plant succession.

Question 37.
Define

1. Hydrosere
2. Xerosere

Answer:

1. Hydrosere: Succession of plants in a freshwater ecosystem.
2. Xerosere: Succession of plants in areas with minimal amount of water.

3 – Mark Questions

Question 38.
What is secondary productivity? Explain its types.
Answer:
The amount of energy stored in the tissues of heterotrophs or consumers is called secondary productivity.

1. Gross secondary productivity: It is equivalent to the total amount of plant material ingested by the herbivores minus the materials lost as faces.
2. Net secondary productivity : Storage of energy or biomass by consumers per unit area per unit time, after respiratory loss is called net secondary productivity.

Question 39.
List the factors affecting primary productivity.
Answer:
Primary productivity depends upon the plant species of an area, their photosynthetic capacity, availability of nutrients, solar radiation, precipitation, soil type, topographic factors (altitude, latitude and direction), and other environmental factors.

Question 40.
Give an account on the concept of trophic level in an ecosystem.
Answer:
A trophic level refers to the position of an organism in the food chain. The number of trophic levels is equal to the number of steps in the food chain. The green plants (producers) occupying the first trophic level (T₁) are called producers. The energy produced by the producers is utilized by the plant eaters (herbivores) they are called primary consumers and occupies the second trophic level (T₂).

Herbivores are eaten by carnivores, which occupy the third trophic level (T₃). They are also called secondary consumers or primary carnivores. Carnivores are eaten by the other carnivores, which occupy the fourth trophic level (T₄). They are called the tertiary consumers or secondary carnivores. Some organisms which eat both plants and animals are called as omnivores (Crow). Such organisms may occupy more than one trophic level in the food chain.

Question 41.
State the second law of thermodynamics.
Answer:
Second law of thermodynamics states that energy transformation results in the reduction of the free energy of the system. Usually energy transformation cannot be 100% efficient. As energy is transferred from one organism to another in the form of food, a portion of it is stored as energy in living tissue, whereas a large part of energy is dissipated as heat through respiration. The transfer of energy is irreversible natural process.

Question 42.
Explain Grazing food chain with example.
Answer:
Main source of energy for the grazing food chain is the Sun. It begins with the first link, producers (plants). The second link in the food chain is primary consumers (mouse) which get their food from producers. The third link in the food chain is secondary consumers (snake) which get their food from primary consumers. Fourth link in the food chain is tertiary consumers (eagle) which get their food from secondary consumers.
Grass → Mouse → Snake → Eagle
Producers Primary consumers Secondary Consumers Tertiary consumers

Question 43.
Write a brief note on Detritus food chain.
Answer:
Detritus food chain is a type of food chain which begins with dead organic matter which is an important source of energy. A large amount of organic matter is derived from the dead plants, animals and their excreta. This type of food chain is present in all ecosystems. The transfer of energy from the dead organic matter, is transferred through a series of organisms called detritus consumers (detritivores)- small carnivores – large (top) carnivores with repeated eating and being eaten respectively. This is called the detritus food chain.
Fallen leaves → Earthworm → Blackbird → Hawk
Detritus Detritivores Small carnivores Top carnivores

Question 44.
Enumerate the significance of food webs.
Answer:
Significance of food web

1. Food web is constructed to describe species interaction called direct interaction.
2. It can be used to illustrate indirect interactions among different species.
3. It can be used to study bottom-up or top-down control of community structure.
4. It can be used to reveal different patterns of energy transfer in terrestrial and aquatic ecosystems.

Question 45.
Name the three types of ecological pyramids.
Answer:

1. pyramid of number
2. pyramid of biomass
3. pyramid of energy.

Question 46.
Spindle shaped pyramid of number is noticed in forest ecosystem. Give reasons.
Answer:
In a forest ecosystem the pyramid of number is spindle in shape, it is because the base (T₁) of the pyramid occupies large sized trees (Producer) which are lesser in number. Herbivores (T₂) (Fruit eating birds, elephant and deer) occupying second trophic level, are more in number than the producers. In final trophic level (T₄), tertiary consumers (lion) are lesser in number than the secondary consumer (T₃) (fox and snake).

Question 47.
Pyramid of energy is always upright – Justify.
Answer:
A graphical representation of energy flow at each successive trophic level in an ecosystem is called pyramids of energy. The bottom of the pyramid of energy is occupied by the producers. There is a gradual decrease in energy transfer at successive tropic levels from producers to the upper levels. Therefore, the pyramid of energy is always upright.

Question 48.
What does the term ‘Eluviation’ stands for?
Answer:
The movement of decomposed, water soluble organic and inorganic compounds from the surface to the lower layer of soil or the carrying away of the same by water is called leaching or eluviation.

Question 49.
What is biogeochemical cycle? Explain its types.
Answer:
Circulation of nutrients within the ecosystem or biosphere is known as biogeochemical cycles and also called as cycling of materials.
There are two basic types:

1. Gaseous cycle – It includes atmospheric Oxygen, Carbon and Nitrogen cycles.
2. Sedimentary cycle – It includes the cycles of Phosphorus, Sulphur and Calcium – Which are present as sediments of Earth.

Question 50.
Explain the cycling of phosphorus in an ecosystem.
Answer:
Phosphorus cycle is a type of sedimentary cycle in which phosphorus is found in the biomolecules like DNA, RNA, ATP, NADP and phospholipid molecules of living organisms. Phosphorus is not abundant in the biosphere, whereas a bulk quantity of phosphorus is present in rock deposits, marine sediments and guano. It is released from these deposits by weathering process.

After that, it circulates in lithosphere as well as hydrosphere. The producers absorb phosphorus in the form of phosphate ions, and then it is transferred to each trophic level of food chain through food. Again death of the organisms and degradation by the action of decomposers, the phosphorus is released back into the lithosphere and hydrosphere to maintain phosphorus cycle.

Question 51.
Discuss the three zones of a lentic ecosystem.
Answer:
There are three zones, littoral, limnetic and profundal. The littoral zone, which is closest to the shore with shallow water region, allows easy penetration of light. It is warm and occupied by rooted plant species. The limnetic zone refers the open water of the pond with an effective penetration of light and domination of planktons.

The deeper region of a pond below the limnetic zone is called profundal zone with no effective light penetration and predominance of heterotrophs. The bottom zone of a pond is termed benthic and is occupied by a community of organisms called benthos (usually decomposers).

Question 52.
What is ecosystem services? Why it is of much importance?
Answer:
Ecosystem services are defined as the benefits that people derive from nature. Study on ecosystem services acts as an effective tool for gaining knowledge on ecosystem benefits and their sustained use. Without such knowledge gain, the fate of any ecosystem will be at stake and the benefits they provide to us in future will become bleak.

Question 53.
Point out any three mangrove ecosystem services.
Answer:

1. Act as bridge between sea and rivers by balancing sedimentation and soil erosion.
2. Help to reduce water force during cyclones, tsunamis and high tide periods.
3. Help in wind break, O₂ production, carbon sequestration and prevents salt spray from waves.

Question 54.
What are the human activities that disturb an ecosystem?
Answer:

1. Habitat destruction.
2. Deforestation and over grazing.
3. Erosion of soils.
4. Introduction of non-native species.
5. Over harvesting of plant material.
6. Pollution of land, water and air.
7. Rim off pesticides, fertilizers and animal wastes.

Question 55.
What is primary succession?
Answer:
The development of plant community in a barren area where no community existed before is called primary succession. The plants which colonize first in a barren area is called pioneer species or primary community or primary colonies. Generally, Primary succession takes a very long time for the occurrence in any region.
Example: Microbes, Lichen and Mosses.

5 – Mark Questions

Question 56.
Describe the various stages of decomposition process.
Answer:

1. Fragmentation – The breaking down of detritus into smaller particles by detritivores like bacteria, fungi and earth worm is known as fragmentation. These detritivores secrete certain substances to enhance the fragmentation process and increase the surface area of detritus particles.
2. Catabolism – The decomposers produce some extracellular enzymes in their surroundings to break down complex organic and inorganic compounds in to simpler ones. This is called catabolism
3. Leaching or Eluviation – The movement of decomposed, water soluble organic and inorganic compounds from the surface to the lower layer of soil or the carrying away of the same by water is called leaching or eluviation.
4. Humification – It is a process by which simplified detritus is changed into dark coloured amorphous substance called humus. It is highly resistant to microbial action, therefore
   decomposition is very slow. It is the reservoir of nutrients.
5. Mineralisation – Some microbes are involved in the release of inorganic nutrients from the humus of the soil, such process is called mineralisation.

Question 57.
Give a detailed account of Biotic and abiotic components of a pond ecosystem. Abiotic components
Answer:
A pond ecosystem consists of dissolved inorganic (CO₂, O₂, Ca, N and Phosphate) and organic substances (amino acids and humic acid) formed from the dead organic matter. The function of pond ecosystem is regulated by few factors like the amount of light, temperature, pH value of water and other climatic conditions.

Biotic components:
They constitute the producers, variety of consumers and decomposers (microorganisms).

(a) Producers: A variety of phytoplanktons like Oscillatoria, Anabaena, Eudorina, Volvox and Diatoms. Filamentous algae such as Ulothrix, Spirogyra, Cladophora and Oedogonium; floating plants Azolla, Salvia, Pistia, Wolffia and Eichhornia; sub-merged plants Potamogeton and Phragmitis; rooted floating plants Nymphaea and Nelumbo; macrophytes like Typha and Ipomoea, constitute the major producers of a pond ecosystem.

(b) Consumers: The animals represent the consumers of a pond ecosystem include zooplanktons like Paramoecium and Daphnia (primary consumers); benthos (bottom living animals) like molluscs and annelids; secondary consumers like water beetles and frogs; and tertiary consumers (carnivores) like duck, crane and some top carnivores which include large fish, hawk and man, etc.

(c) Decomposers: They are also called as microconsumers. They help to recycle the nutrients in the ecosystem. These are present in mud water and bottom of the ponds. Example: Bacteria and Fungi. Decomposers perform the process of decomposition in order to enrich the nutrients in the pond ecosystem.

Question 58.
What are the strategies of eco system management?
Answer:
Strategy of ecosystem management

1. It is used to maintain biodiversity of ecosystems.
2. It helps in indicating the damaged ecosystem (Some species indicate the health of the ecosystem: such species are called a flagship species).
3. It is used to recognize the inevitability of ecosystem change and plan accordingly.
4. It is one of the tools used for achieving sustainability of ecosystem through sustainable development programme (or projects).
5. It is also helpful in identifying ecosystems which are in need of rehabilitation.
6. It involves collaborative management with government agencies, local population, communities and NGO’s.
7. It is used to build the capacity of local institutions and community groups to assume responsibility for long term implementation of ecosystem management activities even after, the completion of the project.

Question 59.
List the characteristics of ecological succession.
Answer:

1. It is a systematic process which causes changes in specific structure of plant community.
2. It is resultant of changes of abiotic and biotic factors.
3. It transforms unstable community into a stable community.
4. Gradual progression in species diversity, total biomass, niche specialisation, and humus content of soil takes place.
5. It progresses from simple food chain to complex food web.
6. It modifies the lower and simple life form to the higher life forms.
7. It creates inter-dependence of plants and animals.

Question 60.
Differentiate Primary succession and Secondary succession
Answer:
Primary succession:

1. Developing in an barren area.
2. Initiated due to a biological or any other external factors.
3. No soil, while primary succession starts
4. Pioneer species come from outside environment.
5. It takes more time to complete.

Secondary succession:

1. Developing in disturbed area.
2. Starts due to external factors only.
3. It starts where soil covers is already present.
4. Pioneer species develop from existing environment.
5. It takes comparatively less time to complete.

Question 61.
Write in detail about Autogenic succession and Allogenic succession.
Answer:
Autogenic succession
Autogenic succession occurs as a result of biotic factors. The vegetation reacts with its environment and modifies its own environment causing its own replacement by new communities. This is known as autogenic succession.
Example: In forest ecosystem, the larger trees produce broader leaves providing shade to the forest floor area. It affects the shrubs and herbs which require more light (heliophytes) but supports the shade tolerant species (sciophytes) to grow well.

Allogenic succession:
Allogenic succession occurs as a result of abiotic factors. The replacement of existing community is caused by other external factors (soil erosion and leaching, etc) and not by existing organisms.
Example: In a forest ecosystem soil erosion and leaching alter the nutrient value of the soil leading to the change of vegetation in that area.

Question 62.
What are the significance of plant succession?
Significance of Plant Succession
Answer:

1. Succession is a dynamic process. Hence an ecologist can access and study the serai stages of a plant community found in a particular area.
2. The knowledge of ecological, succession helps to understand the controlled growth of one or more species in a forest.
3. Utilizing the knowledge of succession, even dams can be protected by preventing siltation.
4. It gives information about the techniques to be used during reforestation and afforestation.
5. It helps in the maintenance of pastures.
6. Plant succession helps to maintain species diversity in an ecosystem.
7. Patterns of diversity during succession are influenced by resource availability and disturbance by various factors.
8. Primary succession involves the colonization of habitat of an area devoid of life.
9. Secondary succession involves the re-establishment of a plant community in disturbed area or habitat.
10. Forests and vegetation that we come across all over the world are the result of plant succession.

Higher Order Thinking Skills (HOTs) Questions

Question 1.
Nutrients are retained in the ecosystem. Discuss how and name the process through which it is achieved?
Answer:
Nutrients will retain in the ecosystem through biogeo chemical cycles. Various nutrients present in soil and atmosphere enter the organism at various trophic levels through food and other process and are cycled back to their origin. Thus the nutrients are not lost but retained in the ecosystem.

Question 2.
According to ten percent law, how many Joules of energy does the individuals at the fourth tropic level will receive; if the individuals at first trophic level receives 1000 Joules of energy?
Answer:
Organism at T₄ level will receive 0.1 Joule of energy as per ten percent law.

Question 3.
Frame any two food chain patterns from the given organisms. Each chain must contain a minimum of four organisms.
Diatoms, Hawk, Rabbit, Vallisneria Stoke, guppies, grass, snake, large fishes, grasshopper, crane.
Answer:

1. Diatom → Guppies → Large fishes → Crane
2. Grass → Rabbit → Snake → Hawk

Question 4.
Mention any two vital biomolecules that requires phosphorous for their biosynthesis.
Answer:
DNA and ATP

Question 5.
The below diagramatic sketch shows the stratisfication of pond ecosystem. Considering it, name X and Y.
Answer:

Diagrammatic sketch shows strarification of Pond ecosystem
X – Limnetic Zone
Y – Benthic Zone

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Samacheer Kalvi 12th Bio Botany Environmental Issues Text Book Back Questions and Answers

Question 1.
Which of the following would most likely help to slow down the greenhouse effect?
(a) Converting tropical forests into grazing land for cattle.
(b) Ensuring that all excess paper packaging is buried to ashes.
(c) Redesigning landfill dumps to allow methane to be collected.
(d) Promoting the use of private rather than public transport.
Answer:
(d) Promoting the use of private rather than public transport.

Question 2.
With respect to Eichhornia
Statement A: It drains off oxygen from water and is seen growing in standing water.
Statement B: It is an indigenous species of our country.
(a) Statement A is correct and Statement B is wrong.
(b) Both Statements A and B are correct.
(c) Statement A is correct and Statement B is wrong.
(d) Both statements A and B are wrong.
Answer:
(a) Statement A is correct and Statement B is wrong.

Question 3.
Find the wrongly matched pair.
(a) Endemism – Species confined to a region and not found anywhere else.
(b) Hotspots – Western ghats
(c) Ex-situ Conservation – Zoological parks
(d) Sacred groves – Saintri hills of Rajasthan
(e) Alien sp Of India – Water hyacinth
Answer:
(d) Sacred groves – Saintri hills of Rajasthan

Question 4.
Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancer?
(a) Ammonia
(b) Methane
(c) Nitrous oxide
(d) Ozone
Answer:
(d) Ozone

Question 5.
One green house gas contributes 14% of total global warming and another contributes 6%. These are respectively identified as ________
(a) N₂O and CO₂
(b) CFCs and N₂O
(c) CH₄ and CO₂
(d) CH₄ and CFCS
Answer:
(b) CFCs and N₂O

Question 6.
One of the chief reasons among the following for the depletion in the number of species making endangered is ______
(a) over hunting and poaching
(b) green house effect
(c) competition and predation
(d) habitat destruction
Answer:
(d) habitat destruction

Question 7.
Deforestation means ______
(a) growing plants and trees in an area where there is no forest
(b) growing plants and trees in an area where the forest is removed
(c) growing plants and trees in a pond
(d) removal of plants and trees
Answer:
(d) removal of plants and trees

Question 8.
Deforestation does not lead to _______
(a) Quick nutrient cycling
(b) Soil erosion
(c) alternation of local weather conditions
(d) Destruction of natural habitat weather conditions
Answer:
(a) Quick nutrient cycling

Question 9.
The unit for measuring ozone thickness ______
(a) Joule
(b) Kilos
(c) Dobson
(d) Watt
Answer:
(c) Dobson

Question 10.
People’s movement for the protection of environment in Sirsi of Karnataka is ________
(a) Chipko movement
(b) Amirtha Devi Bishwas movement
(c) Appiko movement
(d) None of the above
Answer:
(c) Appiko movement

Question 11.
The plants which are grown in silivpasture system are ________
(a) Sesbania and Acacia
(b) Solenum and Crotalaria
(c) Clitoria and Begonia
(d) Teak and sandal
Answer:
(a) Sesbania and Acacia

Question 12.
What is ozone hole?
Answer:
The decline in the thickness of the ozone layer over restricted area is called Ozone hole.

Question 13.
Give four examples of plants cultivated in commercial agroforestry.
Answer:
Casuarina, Eucalyptus, Teak, Malai vembu.

Question 14.
Expand CCS.
Answer:
Carbon Capture and Storage.

Question 15.
Hpw do forests help in maintaining the climate?
Answer:
Forests play a major role in regulating the CO₂ level in the atmosphere. As the result global warming in highly reduced.

Question 16.
How do sacred groves help in the conservation of biodiversity?
Answer:
These are the patches or grove of cultivated trees which are community protected and are based on strong religious belief systems which usually have a significant religious connotation for protecting community. Each grove is an abode of a deity mostly village God Or Goddesses like Aiyanar or Amman.

448 grooves were documented throughout Tamil Nadu, of which 6 groves (Banagudi shola, Thirukurungudi and Udaiyankudikadu, Sittannnavasal, Puthupet and Devadanam) were taken up for detailed floristic and faunistic studies. These groves provide a number of ecosystem services to the neighbourhood like protecting watershed, fodder, medicinal plants and micro climate control.

Question 17.
Which one gas is most abundant out of the four commonest greenhouse gases? Discuss the effect of this gas on the growth of plants?
Answer:
Carbondioxide is the most abundant greenhouse gas. Increase in CO₂ level in the air decreases the uptake of nitrogen components leading to protein deficiency and chlorophyll formation.

Question 18.
Suggest a solution to water crisis and explain its advantages.
Answer:
Rainwater harvesting is the accumulation and storage of rain water for reuse in-site rather than allowing it to run off. Rainwater can be collected from rivers, roof tops and the water collected is directed to a deep pit. The water percolates and gets stored in the pit. RWH is a sustainable water management practice implemented not only in urban area but also in agricultural fields, which is an important economical cost effective method for the future. Environmental benefits of Rain Water Harvesting:

1. Promotes adequacy of underground water and water conservation.
2. Mitigates the effect of drought.
3. Reduces soil erosion as surface run-off is reduced.
4. Reduces flood hazards.
5. Improves groundwater quality and water table / decreases salinity.
6. No land is wasted for storage purpose and no population displacement is involved.
7. Storing water underground is an eco-friendly measure and a part of sustainable water storage strategy for local communities.

Question 19.
Explain afforestation with case studies.
Answer:
Afforestation is planting of trees where there was no previous tree coverage and the conversion of non-forested lands into forests by planting suitable trees to retrieve the vegetation. Example: Slopes of dams afforesed to reduce water run-off, erosion and siltation. It can also provide a range of environmental sendees including carbon sequestration, water retention. The Man who Single Handedly Created a Dense Forest

Jadav “Molai” Payeng (bom 1963) is an environmental activist has single-handedly planted a forest in the middle of a barren wasteland. This Forest Man of India has transformed the world’s largest river island, Majuli, located on one of India’s major rivers, the Brahmaputra, into a dense forest, home to rhinos, deers, elephants, tigers and birds. And today his forest is larger than Central Park.

Former vice-chancellor of Jawahar Lai Nehru University, Sudhir Kumar Sopory named Jadav Payeng as Forest Man of India, in the month of October 2013. He was honoured at the Indian Institute of Forest Management during their annual event Coalescence. In 2015, he was honoured with Padma Shri, the fourth highest civilian award in India. He received honorary doctorate degree from Assam Agricultural University and Kaziranga University for his contributions.

Question 20.
What are the effects of deforestation and benefits of agroforesty?
Answer:
Effects of deforestation:

1. Burning of forest wood release stored carbon, a negative impact just opposite of carbon sequestration.
2. Trees and plants bind the soil particles. The removal of forest cover increases soil erosion and decreases soil fertility. Deforestation in dry areas leads to the formation of deserts.
3. The amount of runoff water increases soil erosion and also creates flash flooding, thus reducing moisture and humidity.
4. The alteration of local precipitation patterns leading to drought conditions in many regions. It triggers adverse climatic conditions and alters water cycle in ecosystem.
5. It decreases the bio-diversity significantly as their habitats are disturbed and disruption of natural cycles.
6. Loss of livelihood for forest dwellers and rural people.
7. Increased global warming and account for one-third of total CO₂ emission.
8. Loss of life support resources, fuel, medicinal herbs and wild edible fruits.

Benefits of agroforestry:

1. It is an answer to the problem of soil and water conservation and also to stabilise the soil (salinity and water table) reduce landslide and water run-off problem.
2. Nutrient cycling between species improves and organic matter is maintained.
3. Trees provide micro climate for crops and maintain CO₂ balanced, atmospheric temperature and relative humidity.
4. Suitable for dry land where rainfall is minimum and hence it is a good system for alternate land use pattern.
5. Multipurpose tree varieties like Acacia are used for wood pulp, tanning, paper and firewood – industries.
6. Agro-forestry is recommended for the following purposes. It can be used as Farm Forestry for the extension of forests, mixed forestry, shelter belts and linear strip plantation.

Samacheer Kalvi 12th Bio Botany Environmental Issues Additional Questions and Answers

1 – Mark Questions

Question 1.
Which is not a green house gas?
(a) CO₂
(b) N₂O
(c) O₃
(d) CFC
Answer:
(C) O₃

Question 2.
Identify the incorrect statement with regard to Global warming.
(a) Leads to species enrichment
(b) Decreases irrigation
(c) Increases vector population
(d) Frequent heat waves
Answer:
(a) Leads to species enrichment

Question 3.
__________ is the unit of measurement of total ozone.
Answer:
Dobson unit

Question 4.
The total ozone layer over the earth surface is __________
(a) 30 DU
(b) 300 DU
(c) 3000 DU
(d) 0.3 DU
Answer:
(b) 300 DU

Question 5.
Methane is __________ times as effective as CO₂ at trapping heat.
(a) 5
(b) 10
(c) 20
(d) 100
Answer:
(b) 20

Question 6.
Which is not a beneficial aspect of Agroforestry?
(a) Nutrient cycling is improved
(b) Balance in O₂ – CO₂ composition
(c) Suitable for wet land where rainfall is maximum
(d) Reduces water run-off problem
Answer:
(c) Suitable for wet land where rainfall is maximum

Question 7.
The production of woody plants combined with pasture is referred to system.
Answer:
Silvopasture

Question 8.
Assertion (A): CO₂ is a main cause for global warming
Reason (R) : Greenhouse gases trap the radiant heat from sun
(a) A is correct R is incorrect.
(b) A is incorrect R is correct.
(c) R explains A.
(d) Both A and R are incorrect.
Answer:
(c) R explains A.

Question 9.
Assertion (A): Ozone acts as a natural sun block.
Reason (R): UV rays reaching the earth are deviated from earth.
(a) A is correct R is incorrect.
(b) A is incorrect R is correct.
(c) R explains A.
(d) Both A and R are incorrect.
Answer:
(c) R explains A.

Question 10.
Assertion (A): Social forestry refers to management of forests and afforestation on barren lands.
Reason (R): Afforestation involves the cutting of trees.
(a) A is correct R is incorrect.
(b) A is incorrect R is correct.
(c) R explains A.
(d) Both A and R are incorrect.
Answer:
(a) A is correct R is incorrect.

Question 11.
Assertion (A): Prosopis juliflora is native to Afganisthan.
Reason (R): Alien species refers to non-native species.
(a) A is correct R is incorrect.
(b) A is incorrect R is correct.
(c) R explains A.
(d) Both A and R are incorrect.
Answer:
(b) A is incorrect R is correct.

Question 12.
Assertion (A): In zoological parks, the animals are maintained in their natural habitat.
Reason (R): Ex-situ conservation refers to protecting species in their natural habitat.
(a) A is correct R is incorrect.
(b) A is incorrect R is correct.
(c) R explains A.
(d) Both A and R are incorrect.
Answer:
(d) Both A and R are incorrect.

Question 13.
Which is not reduced by deforestation?
(a) Amount of habitat
(b) Amount of animal population
(c) Amount of biodiversity
(d) Amount of agricultural land
Answer:
(d) Amount of agricultural land

Question 14.
Identify the potent cause for deforestation.
(a) Agriculture
(b) Soil erosion
(c) Afforestation
(d) Forest fire
Answer:
(a) Agriculture

Question 15.
Total number of forestry extension centres in Tamil Nadu is __________
(a) 16
(b) 32
(c) 18
(d) 51
Answer:
(b) 32

Question 16.
Who is celebrated as Forest Man of India?
(a) Anand Mohan Chakrabarthy
(b) Dr. M.S Swaminathan
(c) Jadav Molai Payeng
(d) Choudary Ram Dhan
Answer:
(c) Jadav Molai Payeng

Question 17.
Invasive species __________
(a) alter the soil system
(b) are more adapted
(c) are fast growing
(d) all the above
Answer:
(d) all the above

Question 18.
Pick out the odd one out __________
(a) Biosphere reserve
(b) National Park
(c) Wild life sanctuaries
(d) Botanical gardens
Answer:
(d) Botanical gardens

Question 19.
Which is not true with respect to prosopis juliflora?
(a) Invasive species native to Mexico
(b) Arrest wind erosion
(c) Absorb hazardous chemical from soil
(d) Decreases O₂ content of water bodies
Answer:
(d) Decreases O₂ content of water bodies

Question 20.
How many numbers of scared grooves were documented in tamil nadu?
(a) 484
(b) 844
(c) 488
(d) 448
Answer:
(c) 488

Question 21.
Match the following:

Answer:
(a) A – iii, B – iv, C – i, D – ii

Question 22.
Process of heating biomass in low oxygen environment is called as ______
Answer:
Pyrolysis

Question 23.
Biochar is __________
(i) a kind of char coal used as a soil amendment
(ii) a potent way of sequestring carbon
(iii) made from biomass via pyrolysis
(iv) a notable solid, rich in carbon.
(a) (i) and (iii) is correct
(b) (ii) and (iv) is correct
(c) (i) and (ii) is correct
(d) all the above is correct.
Answer:
(d) all the above is correct.

Question 24.
Which is not a true statement regarding rain water harvesting?
(a) Mitigates groundwater quality
(b) Reduces soil erosion
(c) Decreases soil salinity
(d) No wastage of land for storing
Answer:
(a) Mitigaes groundwater quality

Question 25.
EIA stands for __________
(a) Ecological Information Analysis
(b) Environmental Information Assessment
(c) Environmental Impact Analysis
(d) Environmental Impact Assessment
Answer:
(d) Environmental Impact Assessment

Question 26.
__________ is the 100th Satellite launched to watch border surveillance.
(a) GSAT-6A
(b) SCAT SAT-I
(c) INSAT 3DR
(d) CARTOSAT-2
Answer:
(d) CARTOSAT-2

Question 27.
The ozone layer of __________ is called bad ozone.
(a) Stratosphere
(b) Mesosphere
(c) Troposphere
(d) Exosphere
Answer:
(c) Troposhere

Question 28.
When does World Ozone Day is observed?
(a) June 17th
(b) December 1st
(c) October 12th
(d) September 16th
Answer:
(d) September 16th

Question 29.
Clean Development Mechanism (CDM) is defined in __________
(a) Copenhagen Acord
(b) Montreal Protocol
(c) Paris Agreement
(d) Kyoto Protocol
Answer:
(d) Kyoto Protocol

Question 30.
__________ is a plant species which acts as an indicator of Nitrate pollution.
(a) Petunia
(b) Lichens
(c) Gladiolus
(d) Pinus
Answer:
(a) Petunia

Question 31.
Identify the plant species that is not used as a live fence.
(a) Sesbania grandiflora
(b) Acacia species
(c) Petunia species
(d) Erythrina species
Answer:
(c) Petunia species

Question 32.
Match the following:

Answer:
(a) A – iv, B – iii, C – ii, D – i

2 – Mark Questions

Question 1.
What are greenhouse gases? Give an example.
Answer:
The gases that capture heat are called Green House Gases.
E.g: Carbon dioxide (CO₂)

Question 2.
Name any four green house gases.
Answer:
CO₂, CH₄, N₂O and CFC

Question 3.
Define global warming.
Answer:
The increase in mean global temperature due to increased concentration of green house gases is called global warming.

Question 4.
Methane is one of a potent green house gas. Point out few sources from where methane is generated.
Answer:
Paddy field, fossil fuel production, bacteria in water bodies, cattle rearing, non-wetland soils and forest & wild fires.

Question 5.
List out the anthropogenic sources of Nitrous oxide.
Answer:
Man-made sources include nylon and nitric acid production, use of fertilizers in agriculture, manures cars with catalytic converter and burning of organic matter.

Question 6.
What is Dobson unit?
Answer:
Dobson Unit is the unit of measurement for total ozone. One DU is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimetre thick at a temperature of 0° C and a pressure of 1 atmosphere.

Question 7.
What do you mean by good ozone and bad ozone?
Answer:

1. The ozone layer of troposphere is called bad ozone.
2. The ozone layer of stratosphere is called good ozone.

Question 8.
What is ozone layer? Why it is essential?
Answer:
Ozone layer is a region of Earth’s stratosphere that absorbs most of the Sim’s ultra violet radiation. The ozone layer is also called as the ozone shield and it acts as a protective shield, cutting the ultra-violet radiation emitted by the sun.

Question 9.
Define ozone hole. Name any one potent chemical that is responsible for the effect.
Answer:
The decline in the thickness of the ozone layer over restricted area is called Ozone hole. Chlorofluorocarbons (CFC) damages the ozone layer to a great extent.

Question 10.
Where did Montreal Protocol was held? State its objectives.
Answer:
The International treaty called the Montreal Protocol (1987) was held in Canada on substances that deplete ozone layer and the main goal of it is gradually eliminating the production and consumption of ozone depleting substances and to limit their damage on the Earth’s ozone layer.

Question 11.
What is meant by biological indicators? Give example.
Answer:
The plant species or plant community acts as a measure of environmental conditions, it is referred as biological indicators or phytoindicators or plant indicators.
E.g: Lichens as SO₂ pollution indicator.

Question 12.
Name the plant species which act as indicators for Nitrate pollution & Flouride pollution.
Answer:

1. Petunia species acts as indicators for Nitrate pollution.
2. Gladiolus species acts as indicators for Flouride pollution.

Question 13.
Define the term Agroforestry. Name any two major tree species cultivated in Agroforestry.
Answer:
Agroforestry is an integration of trees, crops and livestock on the name plot of land. The commercial Agroforestry trees are casuarina and Eucalyptus.

Question 14.
What is silvopasture system? How it helps economy?
Answer:
The production of woody plants combined with pasture is referred to silvopasture system. The trees and shrubs may be used primarily to produce fodder for livestock or they may be grown for timber, fuel wood and fruit or to improve the soil.

Question 15.
Mention the name of any four plant species that are widely used as live fences in agricultural practicer.
Answer:

1. Gliricidia sepium
2. Sesbaniagrandiflora
3. Erythrina species
4. Acacia species

Question 16.
Define social forestry.
Answer:
Social forestry refers to the management of forests and afforestation on barren lands with the purpose of helping the environmental, social and rural development and benefits.

Question 17.
Compare Deforestation and Afforestation
Answer:

1. Deforestation: The conversion of forested area into a non- forested area is known as deforestation.
2. Afforestation: Afforestation is planting of trees where there was no previous tree coverage and the conversion of non-forested lands into forests by planting suitable trees to retrieve the vegetation.

Question 18.
What is invasive species?
Answer:
A non-native species to the ecosystem or country under consideration that spreads naturally, interferes with the biology and existence of native species, poses a serious threat to the ecosystem and causes economic loss

Question 19.
Point out the adverse effect caused by invasive species.
Answer:
Invasive species are fast growing and are more adapted. They alter the soil system by changing litter quality thereby affecting the soil community, soil fauna and the ecosystem processes. It has a negative impact on decomposition in the soils by causing stress to the neighbouring native species.

Question 20.
Distinguish between In-situ conservation and Ex-situ conservation.
Answer:
In-situ conservation:

1. Conservation of species in their natural habitat.
2. E.g: Biosphere reserves

Ex-situ conservation:

1. Conservation of species outside their natural habitat.
2. E.g: Zoological parks

Question 21.
Mention any two historical community level conservation movements held for the protection of environment.
Answer:
Chipko Movement and Appiko Movement

Question 22.
Give the names of any four famous sacred grooves in Tamil Nadu.
Answer:

1. Banagudi Shola
2. Thirukurungudi
3. Udaiyankudikadu
4. Sittannavasal

Question 23.
What does the term ‘Endemic’ refers to?
Answer:
Any species found restricted to a specified geographical area is referred to as ENDEMIC.

Question 24.
Name any two endemic trees of Peninsular India.
Answer:

1. Agasthiyamalaia pauciflora
2. Harawickia binata

Question 25.
What is carbon sequestration?
Answer:
Carbon sequestration is the process of capturing and storing CO₂ which reduces the amount of CO₂ in the atmosphere with a goal of reducing global climate change.

Question 26.
Carbon sequestration occurs naturally by plants and oceans. Name any four microalgal species involved in the process.
Answer:

1. Chlorella
2. Scenedesmus
3. Chroococcus
4. Chlamydomonas

Question 27.
Explain the term Carbon sink.
Answer:
Any system having the capacity to accumulate more atmospheric carbon during a given time interval than releasing CO₂.
Example: forest, soil, ocean are natural sinks. Landfills are artificial sinks.

Question 28.
How EIA is beneficial to a society?
The benefits of EIA to society
Answer:

1. A healthier environment
2. Maintenance of biodiversity
3. Decreased resource usage
4. Reduction in gas emission and environment damage

Question 29.
What is GIS?
Answer:
Geographic Information System (GIS) is a computer system for capturing, storing, checking and displaying data related to positions on Earth’s surface. Also to manipulate, analyse, manage and present spacial or geographic data.

3 – Mark Questions

Question 30.
List out the effects of global warming.
Answer:

1. Rise in global temperature which causes sea levels to rise as polar ice caps and glaciers begin to melt causing submergence of many coastal cities in many parts of the world.
2. There will be a drastic change in weather patterns bringing more floods or droughts in some areas.
3. Biological diversity may get modified, some species ranges get redefined. Tropics and sub-tropics may face the problem of decreased food production.

Question 31.
Mention any three sources of carbon dioxide emission.
Answer:

1. Coal based power plants, by the burning of fossil fuels for electricity generation.
2. Combustion of fuels in the engines of automobiles, commercial vehicles and air planes contribute the most of global warming.
3. Agricultural practices like stubble burning result in emission of CO₂.

Question 32.
What are the adverse effects of global warming on plants?
Answer:

1. Low agricultural productivity in tropics
2. Frequent heat waves (Weeds, pests, fungi need warmer temperature)
3. Increase of vectors and epidemics
4. Strong storms and intense flood damage
5. Water crisis and decreased irrigation
6. Change in flowering seasons and pollinators
7. Change in Species distributional ranges
8. Species extinction

Question 33.
Suggest few ways to overcome global warming.
Answer:

1. Increasing the vegetation cover, grow more trees
2. Reducing the use of fossil fuels and green house gases
3. Developing alternate renewable sources of energy
4. Minimising uses of nitrogeneous fertilizers, and aerosols.

Question 34.
Ozone acts a a natural sun screen – Justify.
Answer:
Ozone depletion in the stratosphere results in more UV radiations especially UV B radiations (shortwaves). UV B radiation destroys biomolecules (skin ageing) and damages living tissues. UV – C is the most damaging type of UV radiation, but it is completely filtered by the atmosphere (ozone layer). UV – a contribute 95% of UV radiation which causes tanning burning of skin and enhancing skin cancer. Hence the uniform ozone layer is critical for the wellbeing of life on earth.

Question 35.
Give a detailed account on clean development mechanism.
Answer:
Clean Development Mechanism (CDM) is defined in the Kyoto protocol (2007) which provides project based mechanisms with two objectives to prevent dangerous climate change and to reduce green house gas emissions. CDM projects helps the countries to reduce or limit emission and stimulate sustainable development.

An example for CDM project activity, is replacement of conventional electrification projectswith solar panels or other energy efficient boilers. Such projects can earn Certified Emission I Reduction (CER) with credits / scores, each equivalent to one tonne of CO₂, which can be counted towards meeting Kyoto targets.

Question 36.
What are the major activities carried out by forestry extension centres?
Answer:

1. Training on tree growing methods
2. Publicity and propaganda regarding tree growing
3. Formation of demonstration plots
4. Raising and supply of seedlings on subsidy
5. Awareness creation among school children and youth about the importance of forests through training and camps.

Question 37.
Prosopis juliflora, though an alien invasive species to India, it is beneficial to certain extent. Give reason.
Answer:
Prosopis juliflora is used to arrest wind erosion and stabilize sand dunes on coastal and desert areas. It can absorb hazardous chemicals from soil and it is the main source of charcoal.

Question 38.
Write a short note on Chipko Movement.
Chipko Movement:
Answer:
The tribal women of Himalayas protested against the exploitation of forests in 1972. Later on it transformed into Chipko Movement by Sundarlal Bahuguna in Mandal village of Chamoli district in 1974. People protested by hugging trees together which were felled by a sports goods company. Main features of Chipko movement were,

1. This movement remained non political
2. It was a voluntary movement based on Gandhian thought.
3. It was concerned with the ecological balance of nature
4. Main aim of Chipko movement was to give a slogan of five Fs – Food, Fodder, Fuel, Fibre and Fertilizer, to make the communities self sufficient in all their basic needs.

Question 39.
Give a brief account on In-situ conservation.
Answer:
In-situble conservation means conservation and management of genetic resources in their natural habitats. Here the plant or animal species are protected within the existing habitat. Forest trees, medicinal and aromatic plants under threat are conserved by this method. This is carried out by the community or by the State conservation which include wildlife, National park and Biosphere reserve. The ecologically unique and biodiversity rich regions are legally protected as wildlife sanctuaries, National parks and Biosphere reserves. Megamalai, Sathyamangalam wildlife, Guindy and Periyar National park, and Western ghats, Nilgiris, Agasthyamalai and Gulf of Mannar are the biosphere reserves of Tamil Nadu.

Question 40.
What do you mean by Biochar? How it helps the environment?
Answer:
Biochar is a long term method to store carbon. To increase plants ability to store more carbon, plants are partly burnt such as crop waste, waste woods to become carbon rich slow decomposing substances of material called Biochar. It is a kind of charcoal used as a soil amendment. Biochar is a stable solid, rich in carbon and can endure in soil for thousands of years. Like most charcoal, biochar is made from biomass via pyrolysis. (Heating biomas in low oxygen environment) which arrests wood from complete burning.

Biochar thus has the potential to help mitigate climate change via carbon sequestration. Independently, biochar when added to soil can increase soil fertility of acidic soils, increase agricultural productivity, and provide protection against some foliar and soil borne diseases. It is a good method of preventing waste woods and logs getting decayed instead we can convert them into biochar thus converting them to carbon storage material.

Question 41.
Explain the role of lakes in an ecosystem.
Answer:
Lakes as a storage of rain water provides drinking water, improves ground water level and preserve the fresh water bio-diversity and habitat of the area where in occurs.

In terms of services lakes offer sustainable solutions to key issues of water management and climatic influences and benefits like nutrient retention, influencing local rainfall, removal of pollutants, phosphorous and nitrogen and carbon sequestration.

5 – Mark Questions

Question 42.
List out the major effects of Ozone depletion.
Answer:
The main ozone depletion effects are:

1. Increases the incidence of cataract, throat and lung irritation and aggravation of asthma or emphysema, skin cancer and diminishing the functioning of immune system in human beings.
2. Juvenile mortality of animals.
3. Increased incidence of mutations.
4. In plants, photosynthetic chemicals will be affected and therefore photosynthesis will be inhibited. Decreased photosynthesis will result in increased atmospheric CO₂ resulting in global warming and also shortage of food leading for food crisis.
5. Increase in temperature changes the climate and rainfall pattern which may result in flood / drought, sea water rise, imbalance in ecosystems affecting flora and fauna.

Question 43.
What are the objectives of Afforestation programme?
Answer:
Afforestation Objectives:

1. To increase forest cover, planting more trees, increases CO₂ production and air quality.
2. Rehabilitation of degraded forests to increase carbon fixation and reducing CO₂ from atmosphere.
3. Raising bamboo plantations.
4. Mixed plantations of minor forest produce and medicinal plants.
5. Regeneration of indigenous herbs / shrubs.
6. Awareness creation, monitoring and evaluation.
7. To increase the level and availability of water table or ground water and also to reduce nitrogen leaching in soil and nitrogen contamination of drinking water, thus making it pure not polluted with nitrogen.
8. Nature aided artificial regeneration.

Question 44.
How Eichhornia crassiper spoils the Indian ecosystem?
Answer:
Eichhornia crassipes is an invasive weed native to South America. It was introduced as aquatic ornamental plant, which grows faster throughout the year. Its widespread growth is a major cause of biodiversity loss worldwide. It affects the growth of phytoplanktons and finally changing the aquatic ecosystem.

It also decreases the oxygen content of the waterbodies which leads to eutrophication. It poses a threat to human health because it creates a breeding habitat for disease causing mosquitoes (particularly Anopheles) and snails with its free floating dense roots and semi submerged leaves. It also blocks sunlight entering deep and the waer ways hampering agriculture, fisheries, recreation and hydropower.

Question 45.
Write a comparative note on Carbon Foot Print (CFP).
Answer:
Every human activity leaves a mark just like our footprint. This Carbon foot print is the total amount of green house gases produced by human activities such as agriculture, industries, deforestation, waste disposal, buring fossil fuels directly or indirectly. It can be measured for an individual, family, organisation like industries, state level or national level. It is usually estimated and expressed in equivalent tons of CO₂ per year.

The burning of fossil fuels releases CO₂ and other green house gases. In turn these emissions trap solar energy and thus increase the global temperature resulting in ice melting, submerging of low lying areas and inbalance in nature like cyclones, tsunamis and extreme weather conditions.
To reduce the carbon foot print we can follow some practices like

1. Eating indigenous fruits and products
2. Reduce use of your electronic devices
3. Reduce travelling
4. Do not buy fast and preserved, processed, packed foods
5. Plant a garden
6. Less consumption of meat and sea food. Poultry requires little space, nutrients and less pollution comparing cattle farming
7. reduce use of Laptops (when used for 8 hours, it releases nearly 2 kg. of CO₂ annually)
8. Line dry your clothes.
   (Example: If you buy imported fruit like kiwi, indirectly it increases CFP. How? The fruit has travelled a long distance in shipping or airliner thus emitting tons of CO₂)

Question 46.
Write in detail about Remote sensing and its uses.
Answer:
Remote Sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area. It is an tool used in conservation practices by giving exact picture and data on identification of even a single tree to large area of vegetation and wild life for classification of land use patterns and studies, identification of biodiversity rich or less areas for futuristic works on conservation and maintenance of various species including commercial crop, medicinal plants and threatened plants.
Specific uses

1. Helps predicting favourable climate, for the study of spreading of disease and controlling it.
2. Mapping of forest fire and species distribution.
3. Tracking the patterns of urban area development and the changes in Farmland or forests over several years.
4. Mapping ocean bottom and its resources.

Higher Order Thinking Skills (HOTs) Questions

Question 1.
Name the movement launched by the people of Mandal village to protect the trees by hugging them.
Answer:
Chipko movement.

Question 2.
Recently in January 2019, our Tamil Nadu Government had imposed a ban on using 14 different products of plastic origin. Mention any six plastic products that you know.
Answer:

1. Water Packets
2. Plastic straws
3. Plastic carry bags
4. Thermocol cups
5. Plastic coated paper plates
6. Plastic flags.

Question 3.
Due to plastic ban scheme in our state, people are gradually switching over to other optionals for daily activities. As a biology student, suggest few eco-friendly alternatives for this issue.
Answer:

1. Cloth / Jute bags
2. Plantain leave, palmyra plates as plates
3. Metal cups
4. Earthen pots or ceramic wares
5. Paper made flags

Question 4.
Deforestation is creating various adverse effect on environment. Enlist the consequences of deforestation.
Answer:

1. Increased global warming.
2. Loss of livelihood for forest dwellers.
3. Loss of bio-diversity
4. Decrease in soil fertility.
5. Decline in annual rainfall.

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Samacheer Kalvi 12th Physics Recent Developments in Physics Textual Evaluation Solved

Samacheer Kalvi 12th Physics Recent Developments in Physics Multiple Choice Questions

Question 1.
The particle size of ZnO material is 30 nm. Based on the dimension it is classified as –
(a) Bulk material
(b) Nanomaterial
(c) Soft material
(d) Magnetic material.
Answer:
(b) Nanomaterial

Question 2.
Which one of the following is the natural nanomaterial?
(a) Peacock feather
(b) Peacock beak
(c) Grain of sand
(d) Skin of the Whale.
Answer:
(a) Peacock feather

Question 3.
The blue print for making ultra durable synthetic material is mimicked from-
(a) Lotus leaf
(b) Morpho butterfly
(c) Parrot fish
(d) Peacock feather.
Answer:
(c) Parrot fish

Question 4.
The method of making nanomaterial by assembling the atoms is called-
(a) Top down approach
(h) Bottom up approach
(c) Cross down approach
(d) Diagonal approach.
Answer:
(b) Bottom up approach

Question 5.
“Sky wax” is an application of nano product in the field of-
(a) Medicine
(b) Textile
(c) Sports
(d) Automotive industry.
Answer:
(c) Sports

Question 6.
The materials used in Robotics are-
(a) Aluminium and silver
(b) Silver and gold
(c) Copper and gold
(d) Steel and aluminium.
Answer:
(d) Steel and aluminum.

Question 7.
The alloys used for muscle wires in Robots are-
(a) Shape memory alloys
(b) Gold copper alloys
(c) Gold silver alloys
(d) Two dimensional alloys.
Answer:
(a) Shape memory alloys

Question 8.
The technology used for stopping the brain from processing pain is-
(a) Precision medicine
(b) Wireless brain sensor
(c) Virtual reality
(d) Radiology.
Answer:
(c) Virtual reality

Question 9.
The particle which gives mass to protons and neutrons are-
(a) Higgs particle
(b) Einstein particle
(c) Nanoparticle
(d) Bulk particle.
Answer:
(a) Higgs particle

Question 10.
The gravitational waves were theoretically proposed by-
(a) Conrad Rontgen
(b) Marie Curie
(c) Albert Einstein
(d) Edward Purcell.
Answer:
(c) Albert Einstein

Samacheer Kalvi 12th Physics Recent Developments in Physics Short Answer Questions

Question 1.
Distinguish between Nanoscience and Nanotechnology?
Answer:
1. Nanoscience:

• Nanoscience is the science of objects with typical sizes of 1 – 100 nm. Nano means one – billionth of a metre that is 10^-9 m.
• If matter is divided into such small objects the mechanical, electrical, optical, magnetic and other properties change.

2. Nanotechnology:

• Nanotechnology is a technology involving the design, production, characterization, and applications of nano structured materials.

Question 2.
What is the difference between Nano materials and Bulk materials?
Answer:

1. The solids are made up of particles. Each of the particle has a definite number of atoms, which might differ from material to material. If the particle of a solid is of size less than 100 nm, it is said to be a ‘nano solid’.
2. When the particle size exceeds 100 nm, it is a ‘bulk solid’. It is to be noted that nano and bulk solids may be of the same chemical composition.
3. For example, ZnO can be both in bulk and nano form.
4. Though chemical composition is the same, nano form of the material shows strikingly different properties when compared to its bulk counterpart.

Question 3.
Give any two examples for “Nano” in nature.
Answer:
1.  Single strand DNA:
A single strand of DNA, the building block of all living things, is about three nanometers wide.

2. Morpho Butterfly:
The scales on the wings of a morpho butterfly contain nanostructures that change the way light waves interact with each other, giving the wings brilliant metallic blue and green hues. Mimic in laboratories – Manipulation of colours by adjusting the size of nano particles with which the materials are made.

Question 4.
Mention any two advantages and disadvantages of Robotics.
Answer:

1. Advantages of Robotics:
   • The robots are much cheaper than humans.
   • Robots never get tired like humans. It can work for 24 x 7. Hence absenteeism in work place can be reduced.
   • Robots are more precise and error free in performing the task.
2. Disadvantages of Robotics:
   • Robots have no sense of emotions or conscience.
   • They lack empathy and hence create an emotionless workplace.
   • If ultimately robots would do all the work, and the humans will just sit and monitor them, health hazards will increase rapidly.

Question 5.
Why steel is preferred in making Robots?
Answer:
Steel is several time stronger. In any case, because of the inherent strength of metal, robot bodies are made using sheet, bar, rod, channel, and other shapes.

Question 6.
What are black holes?
Answer:
Black holes are end stage of stars which are highly dense massive object. Its mass ranges from 20 times mass of the sun to 1 million times mass of the sun. It has very strong gravitational force such that no particle or even light can escape from it. The existence of black holes is studied when the stars orbiting the black hole behave differently from the other starts. Every galaxy has black hole at its center. Sagittarius A* is the black hole at the center of the Milky Way galaxy.

Question 7.
What are sub atomic particles?
Answer:

1. The three main subatomic particles that form an atom are protons, neutrons and electrons.
2. Subatomic particles are particles that are smaller than the atom, proton and neutron are made up of quarks which is interact through gluons.
3. Subatomic particle having two types of particles, they are elementary particle and composite particle.

Samacheer Kalvi 12th Physics Recent Developments in Physics Long Answer Questions

Question 1.
Discuss the applications of Nanomaterials in various fields?
Answer:
(i) Automotive industry:

• Lightweight construction
• Painting (fillers, base coat, clear coat)
• Catalysts
• Tires (fillers)
• Sensors
• Coatings for window screen and car bodies

(ii) Chemical industry:

• Fillers for paint systems
• Coating systems based on nanocomposites
• Impregnation of papers
• Switchable adhesives
• Magnetic fluids

(iii) Engineering

• Wear protection for tools and machines (anti blocking coatings, scratch resistant coatings on plastic parts, etc.)
• Lubricant – free bearings

(iv) Electronic industry

• Data memory
• Displays
• Laser diodes
• Glass fibres
• Optical switches
• Filters (IR-blocking)
• Conductive, antistatic coatings

(v) Construction:

• Construction materials
• Thermal insulation
• Flame retardants
• Surface – functionalised building materials for wood, floors, stone, facades, tiles, roof tiles, etc.
• Facade coatings
• Groove mortar

(vi) Medicine:

• Drug delivery systems
• Contrast medium
• Prostheses and implants
• Agents in cancer therapy
• Active agents
• Medical rapid tests
• Antimicrobial agents and coatings

(vii) Textile / fabrics / non – wovens:

• Surface – processed textiles
• Smart clothes

(viii) Energy:

• Fuel cells
• Solar cells
• Batteries
• Capacitors

(ix) Cosmetics:

• Sun protection
• Lipsticks
• Skin creams
• Tooth paste

(x) Food and drinks:

• Package materials
• Additives
• Storage life sensors
• Clarification of fruit juices

(xi) Household:

• Ceramic coatings for irons
• Odors catalyst
• Cleaner for glass, ceramic, floor, windows

(xii) Sports / outdoor:

• Ski wax
• Antifogging of glasses / goggles
• Antifouling coatings for ships / boats
• Reinforced tennis rackets and balls.

Question 2.
What are the possible harmful effects of usage of Nanoparticles? Why?
Answer:
Possible harmful effects of usage of Nanoparticles:

1. The research on the harmful impact of application of nanotechnology is also equally important and fast developing. The major concern here is that the nanoparticles have the dimensions same as that of the biological molecules such as proteins. They may easily get absorbed onto the surface of living organisms and they might enter the tissues and fluids of the body.

2. The adsorbing nature depends on the surface of the nanoparticle. Indeed, it is possible to deliver a drug directly to a specific cell in the body by designing the surface of a nanoparticle so that it adsorbs specifically onto the surface of the target cell.

3. The interaction with living systems is also affected by the dimensions of the nanoparticles. For instance, nanoparticles of a few nanometers size may reach well inside biomolecules, which is not possible for larger nanoparticles.

4. Nanoparticles can also cross cell membranes. It is also possible for the inhaled nanoparticles to reach the blood, to reach other sites such as the liver, heart or blood cells.

5. Researchers are trying to understand the response of living organisms to the presence of nanoparticles of varying size, shape, chemical composition and surface characteristics.

Question 3.
Discuss the functions of key components in Robots?
Answer:
The robotic system mainly consists of sensors, power supplies, control systems, manipulators and necessary software. Most robots are composed of 3 main parts:

1. 1. The Controller: Also known as the “brain” which is run by a computer program. It gives commands for the moving parts to perform the job.
   2. Mechanical parts: Motors, pistons, grippers, wheels, and gears that make the robot move, grab, turn, and lift.
   3. Sensors: To tell the robot about its surroundings. It helps to determine the sizes and shapes of the objects around, distance between the objects, and directions as well.
      

Question 4.
Elaborate any two types of Robots with relevant examples?
Answer:
(i) Human Robot: Certain robots are made to resemble humans in appearance and replicate the human activities like walking, lifting, and sensing, etc.

1. Power conversion unit:
   Robots are powered by batteries, solar power, and hydraulics.
2. Actuators:
   Converts energy into movement. The majority of the actuators produce rotational or linear motion.
3. Electric motors:
   They are used to actuate the parts of the robots like wheels, arms, fingers,
   legs, sensors, camera, weapon systems etc. Different types of electric motors are used. The most often used ones are AC motor, Brushed DC motor, Brushless DC motor, Geared DC motor, etc.
4. Pneumatic Air Muscles:
   They are devices that can contract and expand when air is pumped inside. It can replicate the function of a human muscle. They contract almost 40% when the air is sucked inside them.
5. Muscle wires:
   They are thin strands of wire made of shape memory alloys. They can contract by 5% when electric current is passed through them.
6. Piezo Motors and Ultrasonic Motors:
   Basically, we use it for industrial robots.
7. Sensors:
   Generally used in task environments as it provides information of real – time knowledge.
8. Robot locomotion:
   Provides the types of movements to a robot. The different types are:
   • Legged
   • Wheeled
   • Combination of Legged and Wheeled Locomotion
   • Tracked slip / skid.

(ii) Industrial Robots:
Six main types of industrial robots:

1. Cartesian
2. SCARA (Selective Compliance Assembly Robot Arm)
3. Cylindrical
4. Delta
5.  Polar
6. Vertically articulated

Six – axis robots are ideal for:

1. Arc Welding
2. Spot Welding
3. Material Handling
4. Machine Tending
5. Other Applications

Question 5.
Comment on the recent advancement in medical diagnosis and therapy.
Answer:
The recent advancement in medical diagnosis and therapy:

1. Virtual reality
2. Precision medicine
3. Health wearables
4. Artificial organs
5.  3 – D printing
6. Wireless brain sensors
7. Robotic surgery
8. Smart inhalers

1. Virtual reality:
Medical virtual reality is effectively used to stop the brain from processing pain and cure soreness in the hospitalized patients. Virtual reality has enhanced surgeries by the use of 3D models by surgeons to plan operations. It helps in the treatment of Autism, Memory loss, and Mental illness.

2. Precision medicine:
Precision medicine is an emerging approach for disease treatment and prevention that takes into account individual variability in genes, environment, and lifestyle for each person. In this medical model it is possible to customise healthcare, with medical decisions, treatments, practices, or products which are tailored to the individual patient.

3. Health wearables:
A health wearable is a device used for tracking a wearer’s vital signs or health and fitness related data, location, etc. Medical wearables with artificial intelligence and big data provide an added value to healthcare with a focus on diagnosis, treatment, patient monitoring and prevention.

Note: Big Data:Extremely large data sets that may be analysed computationally to reveal patterns, trends, and associations, especially relating to human behaviour and interactions.

4. Artificial organs:
An artificial organ is an engineered device or tissue that is implanted or integrated into a human. It is possible to interface it with living tissue or to replace a natural organ. It duplicates or augments a specific function or functions of human organs so that the patient may return to a normal life as soon as possible.

5. 3D printing:
Advanced 3D printer systems and materials assist physicians in a range of operations in the medical field from audiology, dentistry, orthopedics and other applications.

6. Wireless brain sensors:
Wireless brain sensors monitor intracranial pressure and temperature and then are
absorbed by the body. Hence there is no need for surgery to remove these devices.

7. Robotic surgery:
Robotic surgery is a type of surgical procedure that is done using robotic systems. Robotically – assisted surgery helps to overcome the limitations of pre – existing minimally invasive surgical procedures and to enhance the capabilities of surgeons performing open
surgery.

8. Smart inhalers:
Inhalers are the main treatment option for asthma. Smart inhalers are designed with health systems and patients in mind so that they can offer maximum benefit. Smart inhalers use bluetooth technology to detect inhaler use, remind patients when to take their medication and gather data to help guide care.

Samacheer Kalvi 12th Physics Recent Developments in Physics Additional Questions

Samacheer Kalvi 12th Physics Recent Developments in Physics Multiple Choice Questions

Question 1.
An automatic apparatus or device that performs functions ordinarily ascribed to human or
operate with what appears to be almost human intelligence is called ……………. .
(a) Robot
(b) Human
(c) Animals
(d) Reptiles.
Answer:
(a) Robot.

Question 2.
The laws of Robotics are ……………. .
(a) a robot may not injure a human being
(b) a robot must obey the order given by human
(c) a robot must protect its own existence
(d) both b and c.
Answer:
(d) both b and c.
Hint:
A robot may not injure a human being or through in action, allow human being to be harmed.

Question 3.
The basic components of robot are ……………. .
(a) mechanical linkage
(b) sensors and controllers
(c) user interface and power conversion unit
(d) All the above.
Answer:
(d) All the above.

Question 4.
What is the name for information sent from robot sensors to robot controllers ……………. .
(a) temperature
(b) pressure
(c) feedback
(d) signal.
Answer:
(c) feedback

Question 5.
Which of the following uses radio frequency to produce nano – particles ……………. .
(a) Plasma arching
(b) Chemical vapour deposition
(c) Sol-gel technique
(d) Electro deposition.
Answer:
(a) Plasma arching

Question 6.
Which of the following the atoms do not move from each other ……………. .
(a) Shape memory alloys
(b) Nano materials
(c) Dielectrics
(d) Static materials.
Answer:
(b) Nano materials

Question 7.
The diameter of the nano wire is about ……………. .
(a) 10^-6 m
(b) 10^-3 m
(c) 10^-8 m
(d) 10^-9 m.
Answer:
(d) 10^-9 m.

Question 8.
A suspended nano wire is a wire that is produced in ……………. .
(a) Air medium
(b) Vaccum
(c) Low vaccum chamber
(d) High vaccum chamber.
Answer:
(d) High vaccum chamber.

Question 9.
For nano metres whose diameters less than …………….are used as welding purposes.
(a) 10 nm
(b) 20 nm
(c) 30 nm
(d) 40 nm.
Answer:
(a) 10 nm

Question 10.
Nano wires are used in ……………. .
(a) 10 nm
(b) Resistors
(c) Capacitors
(d) Transducers.
Answer:
(a) 10 nm

Question 11.
Generally what is the material of needle electrodes ……………. .
(a) Stainless steel
(b) Copper
(c) Lead
(d) Iron.
Answer:
(a) Stainless steel

Question 12.
……………. introduced is used to hold patients head and guide the placements of electrodes.
(a) Monotaxic
(b) Stereotonic
(c) Stereotaxic
(d) Monotonic.
Answer:
(c) Stereotaxic

Question 13.
Who is the father of the modem robotics industry formed the world’s first robotic company in 1956 ……………. .
(a) Joliot
(b) Cormark
(c) Engelberger
(d) Edward purcell.
Answer:
(c) Engelberger

Question 14.
In 1954, ……………. invented the first digitally operated programmable robot called unimate.
(a) Edward purcell
(b) George Devol
(c) Engel berger
(d) Joliot.
Answer:
(b) George Devol

Question 15.
The phenomenon of artificial radioactivity was invented by ……………. .
(a) Joliot and Irene curie
(b) Felix Bloch and Edward purcell
(c ) Connack and Hounsfield
(d) Wilhelm conrad – Rontgen.
Answer:
(a) Joliot and Irene curie

Samacheer Kalvi 12th Physics Recent Developments in Physics Short Answer Question

Question 1.
What is physics?
Answer:
Physics is the basic building block for Science, Engineering, Technology and Medicine.

Question 2.
Write down the applications of Nano technology?
Answer:

• Energy storage
• Metallurgy and materials
• Optical engineering and communication
• Agriculture and food
• Biotechnology
• Defense and security Electronics
• Biomedical and drug delivery
• Cosmetics and paints
• Textile.

Question 3.
What is robotics?
Answer:
Robotics is an integrated study of mechanical engineering, electronic engineering, computer engineering, and science.

Question 4.
What is meant by ‘Robot’? Write its uses?
Answer:
Robot is a mechanical device designed with electronic circuitry and programmed to perform a specific task. These automated machines are highly significant in this robotic era where they can take up the role of humans in certain dangerous environments that are hazardous to people like defusing bombs, finding survivors in unstable ruins, and exploring mines and shipwrecks.

Question 5.
What is the meaning of particle physics?
Answer:
Particle physics deals with the theory of fundamental particles of nature and it is one of the active research areas in physics. Initially it was thought that atom is the fundamental entity of matter.

Question 6.
Define cosmology?
Answer:
Cosmology is the branch that involves the origin and evolution of the universe. It deals with formation of stars, galaxy etc.

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Tamilnadu Samacheer Kalvi 12th Physics Solutions Chapter 9 Semiconductor Electronics

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Samacheer Kalvi 12th Physics Semiconductor Electronics Textual Evaluation Solved

Samacheer Kalvi 12th Physics Semiconductor Electronics Multiple Choice Questions

Question 1.
The barrier potential of a silicon diode is approximately,
(a) 0.7 V
(b) 0.3 V
(c) 2.0 V
(d) 2.2 V.
Answer:
(a) 0.7 V

Question 2.
Doping a semiconductor results in
(a) The decrease in mobile charge carriers
(b) The change in chemical properties
(c) The change in the crystal structure
(d) The breaking of the covalent bond.
Answer:
(c) The change in the crystal structure

Question 3.
A forward biased diode is treated as-
(a) An open switch with infinite resistance
(b) A closed switch with a voltage drop of 0V
(c) A closed switch in series with a battery voltage of 0.7V
(d) A closed switch in series with a small resistance and a battery.
Answer:
(d) A closed switch in series with a small resistance and a battery.

Question 4.
If a half – wave rectified voltage is fed to a load resistor, which part of a cycle the load current will flow?
(a) 0° – 90°
(b) 90° – 180°
(c) 0° – 180°
(d) 0° – 360°
Answer:
(c) 0° – 180°

Question 5.
The primary use of a zener diode is-
(a) Rectifier
(b) Amplifier
(c) Oscillator
(d) Voltage regulator.
Answer:
(d) Voltage regulator.

Question 6.
The principle in which a solar cell operates-
(a) Diffusion
(b) Recombination
(c) Photovoltaic action
(d) Carrier flow.
Answer:
(c) Photovoltaic action

Question 7.
The light emitted in an LED is due to-
(a) Recombination of charge carriers
(b) Reflection of light due to lens action
(c) Amplification of light falling at the junction.
Answer:
(a) Recombination of charge carriers

Question 8.
When a transistor is fully switched on, it is said to be-
(a) Shorted
(b) Saturated
(c) Cut – off
(d) Open.
Answer:
(b) Saturated

Question 9.
The specific characteristic of a common emitter amplifier is-
(a) High input resistance
(b) Low power gain
(c) Signal phase reversal
(d) Low current gain.
Answer:
(c) Signal phase reversal

Question 10.
To obtain sustained oscillation in an oscillator,
(a) Feedback should be positive
(b) Feedback factor must be unity
(c) Phase shift must be 0 or 2π
(d) All the above.
Answer:
(d) All the above.

Question 11.
If the input to the NOT gate is A = 1011, its output is?
(a) 0100
(b) 1000
(c) 1100
(d) 0011.
Answer:
(a) 0100

Question 12.
The electrical series circuit in digital form is-
(a) AND
(b) OR
(c) NOR
(d) NAND.
Answer:
(a) AND

Question 13.
Which one of the following represents forward bias diode? (NEET)

Answer:

Question 14.
The given electrical network is equivalent to (NEET)

(a) AND gate
(b) OR gate
(c) NOR gate 1
(d) NOT gate.
Answer:
(c) NOR gate

Question 15.
The output of the following circuit is 1 when the input ABC is (NEET 2016)

(a) 101
(b) 100
(c) 110
(d) 010.
Answer:
(a) 101

Samacheer Kalvi 12th Physics Semiconductor Electronics Short Answer Questions

Question 1.
Define electron motion in a semiconductor?
Answer:
To move the hole in a given direction, the valence electrons move in the opposite direction. Electron flow in an N – type semiconductor is similar to electrons moving in a metallic wire. The N – type dopant atoms will yield electron available for conduction.

Question 2.
Distinguish between intrinsic and extrinsic semiconductors.
Answer:
1. Intrinsic:

• These are pure semiconducting tetravalent crystals.
• Their electrical conductivity is low.
• There is no permitted energy state between valence and conduction band.
• Their electrical conductivity depends on temperature.

2. Extrinsic:

• These are semiconducting tetravalent crystals doped with impurity atoms group III (or) V.
• Their electrical conductivity is high.
• There is no permitted energy state of the impurity atom between valence and conduction band.
• Their electrical conductivity depends on temperature as well as dopant concentration.

Question 3.
What do you mean by doping?
Answer:
The process of adding impurities to the intrinsic semiconductor is called doping.

Question 4.
How electron-hole pairs are created in a semiconductor material?
Answer:
The free electrons from electron hole pairs, enable current to flow in the semiconductor when an external voltage is applied. The holes in the valence band also allow electron movement within the valence band itself and this also contributes to current flow. This process is called electron – hole pair generation.

Question 5.
A diode is called as a unidirectional device. Explain?
Answer:
Diode is called as a unidirectional device, i.e., current flows in only one direction (anode to cathode internally) when a forward voltage is applied, the diode conducts and when reverse voltage is applied, there is no conduction. A mechanical analogy is a rat chat, which allows motion in one direction only.

Question 6.
What do you mean by leakage current in a diode?
Answer:
The leakage current in a diode is the current that the diode will leak when a reverse voltage is applied to it. Under the reverse bias, a very small current in μA, flows across the junction. This is due to the flow of the minority charge carriers called the leakage current or reverse saturation current.

Question 7.
Draw the output waveform of a full wave rectifier.
Answer :

Question 8.
Distinguish between avalanche and zener breakdown.
Answer:
1. Avalanche Breakdown:

• It occurs in junctions which are lightly and have wide depletion widths.
• It occurs at higher reverse voltages when thermally generated electrons get enough kinetic energy to produce more electrons by collision.
• At reverse voltage above 6 V breakdown is due to avalanche effect.
• Electric field produced is weak in nature.
• Charge carriers obtain energy from the applied potential.

2. Zener Breakdown:

• It occurs in junctions which are heavily doped and have narrow depletion widths.
• It occurs due to rupture of covalent bonds by strong electric fields set up in depletion region by the reverse voltage.
• At reverse voltage below 6V breakdown is due to zener effect.
• A strong electric field is produced
• Zener current is independent of applied voltage.

Question 9.
Discuss the biasing polarities in an NPN and PNP transistors.
Answer:
In a PNP transistor, base and collector will be negative with respect to emitter indicated by the middle letter N whereas base and collector will be positive in an NPN transistor [indicated by the middle letter P]

Question 10.
Explain the current flow in a NPN transistor?
Answer:

1. The conventional flow of current is based on the direction of the motion of holes
2. In NPN transistor, current enters from the base into the emitter.

Question 11.
What is the phase relationship between the AC input and output voltages in a common emitter amplifier? What is the reason for the phase reversal?
Answer:
In a common emitter amplifier, the input and output voltages are 180° out of phase or in, opposite phases. The reason for this can be seen from the fact that as the input voltage rises, so the current increases through the base circuit.

Question 12.
Explain the need for a feedback circuit in a transistor oscillator.
Answer:
The circuit used to feedback a portion of the output to the input is called the feedback network. If the portion of the output fed to the input is in phase with the input, then the magnitude of the input signal increases. It is necessary for sustained oscillations.

Question 13.
Give circuit symbol, logical operation, truth table, and Boolean expression of-

1. AND
2. OR
3. NOT
4. NAND
5. NOR
6. EX – OR gates.

Answer:
1. AND gate Circuit symbol:
A and B are inputs and Y is the output.

It is a logic gate and hence A, B, and Y can have the (a) Two input AND gate value of either 1 or 0.

Boolean equation:
Y = A.B
It performs logical multiplication and is
different from arithmetic multiplication.
Logic operation:
The output of AND gate is high (1) only when all the inputs are high (1). The rest of the cases the output is low. Hence the output of AND gate is high (1) only when all the inputs are high.

2. OR gate:
Circuit Symbol
A and B are inputs and Y is the output.

Boolean equation:
A + B = Y
It performs logical addition and is different from arithmetic addition.

Logic operation:
The output of OR gate is high (logic 1 state) when either of the inputs or both are high.

3. NOT gate:
Circuit symbol
A is the input and Y is the output.

Boolean equation:
Y = \(\overline { A } \)

Logic operation:
The output is the complement of the input.

It is represented with an overbar. It is also called as inverter. The truth table infers that the output Y is 1 when input A is 0 and vice versa. The truth table of NOT.

4. NAND gate:
A and B are inputs and Y is the output.

Boolean equation:
Y = Y= \(\overline { AB } \)
Logic operation:
The output Y equals the complement of AND operation. The circuit is an AND gate followed by a NOT gate. Therefore, it is summarized as NAND. The output is at logic zero only when all the inputs are high. The rest of the cases, the output is high (Logic 1 state).

5. NOR gate:
Circuit symbol: A and B are inputs and Y is the output.

Boolean equation:
Y= A + B
Logic operation:
Y equals the complement of OR operation (A OR B). The circuit is an OR gate followed by a NOT gate and is summarized as NOR. The output is high when all the inputs are low. The output is low for all other combinations of inputs.

6. Ex – OR gate:
Circuit symbol
A and B are inputs and Y is the output. The Ex-OR operation is denoted as ⊕.
Boolean equation:
Y = A. \(\overline { B } \) + \(\overline { A } \) .B
Y = A ⊕ B
Logic operation:
The output is high only when either of the two inputs is high. In the case of an Ex-OR gate with more than two inputs, the output will be high when odd number of inputs are high.

Question 14.
State De Morgan’s first and second theorems De Morgan’s First Theorem?
Answer:
The first theorem states that the complement of the sum of two logical inputs is equal to the product of its complements.
\(\overline { A+B } \) = \(\overline { A } \).\(\overline { B } \)
De Morgan’s Second Theorem:
The second theorem states that the complement of the product of two inputs is equal to the sum of its complements.
\(\overline { A.B } \) = \(\overline { A+B } \)

Samacheer Kalvi 12th Physics Semiconductor Electronics Long Answer Questions

Question 1.
Elucidate the formation of a N – type and P – type semiconductors.
Answer:
1. N – type semiconductor:
A n-type semiconductor is obtained by doping a pure Germanium (or Silicon) crystal with a dopant from group V pentavalent elements like Phosphorus, Arsenic, and Antimony. The dopant has five valence electrons while the Germanium atom has four valence electrons.

During the process of doping, a few of the Germanium atoms are replaced by the group V dopants. Four of the five valence electrons of the impurity atom are bound with the 4 valence electrons of the neighbouring replaced Germanium atom. The fifth valence electron of the impurity atom will be loosely attached with the nucleus as it has not formed the covalent bond.

The energy level of the loosely attached fifth electron from the dopant is found just below the conduction band edge and is called the donor energy level. At room temperature, these electrons can easily move to the conduction band with the absorption of thermal energy. It is shown in the figure (c). Besides, an external electric field also can set free the loosely bound electrons and lead to conduction.

It is important to note that the energy required for an electron to jump from the valence band to the conduction band (E_g) in an intrinsic semiconductor is 0.7 eV for Ge and 1.1 eV for Si, while the energy required to set free a donor electron is only 0.01 eV for Ge and 0.05 eV for Si.

The group V pentavalent impurity atoms donate electrons to the conduction band and are called donor impurities. Therefore, each impurity atom provides one extra electron to the conduction band in addition to the thermally generated electrons. These thermally generated electrons leave holes in valence band. Hence, the majority carriers of current in an n-type Semiconductor are electrons and the minority carriers are holes. Such a semiconductor doped with a pentavalent impurity is called an n-type semiconductor.

2. P – type semiconductor:
Here, a trivalent atom from group III elements such as Boron, Aluminium, Gallium and Indium is added to the Germanium or Silicon substrate. The dopant with three valence electrons are bound with the neighbouring Germanium atom as shown in Figure (a). As Germanium atom has four valence electrons, one electron position of the dopant in the Germanium crystal lattice will remain vacant. The missing electron position in the covalent bond is denoted as a hole.

To make complete covalent bonding with all four neighbouring atoms, the dopant is in need of one more electron. These dopants can accept electrons from the neighbouring atoms. Therefore, this impurity is called an acceptor impurity. The energy level of the hole created by each impurity atom is just above the valence band and is called the acceptor-energy level, as shown in Figure (b).

For each acceptor atom, there will be a hole in the valence band in addition to the thermally generated holes. In such an extrinsic semiconductor, holes are the majority carriers and thermally generated electrons are minority carriers. The semiconductor thus formed is called a p – type semiconductor.

Question 2.
Explain the formation of PN junction diode. Discuss its V-I characteristics.
Answer:
Formation of depletion layer:
A p – n junction is formed by joining n-type and p-type semiconductor materials as shown in figure.

(a) Since the n-region has a high electron concentration and the p-region a high hole concentration, electrons diffuse from the n-side to the p-side. This causes diffusion current which exists due to the concentration difference of electrons. The electrons diffusing into the p-region may occupy holes in that region and make it negative.

The holes left behind by these electrons in the n-side are equivalent to the diffusion of holes from the p-side to the n-side. If the electrons and holes were not charged, this diffusion process would continue until the concentration of electrons and holes on the two sides were the same, as happens if two gasses come into contact with each other.

But, in a p – n junction, when the electrons and holes move to the other side of the junction, they leave behind exposed charges on dopant atom sites, which are fixed in the crystal lattice and are unable to move. On the n-side, positive ion cores are exposed and on the p-side, negative ion cores are exposed as shown in Figure

(b) An electric field E forms between the positive ion cores in the n – type material and negative ion cores in the p-type material. The electric field sweeps free carriers out of this region and hence it is called depletion region as it is depleted of free carriers. A barrier potential V_b due to the electric field E is formed at the junction as shown in Figure.

(c) As this diffusion of charge carriers from both sides continues, the negative ions form a layer of negative space charge region along the p-side. Similarly, a positive space charge region is formed by positive ions on the n-side. The positive space charge region attracts electrons from p-side to n-side and the negative space charge region attracts holes from n-side to p-side.

This moment of earners happen in this region due to the formed electric field and it constitutes a current called drift current. The diffusion current and drift current flow in the opposite direction and at one instant they both become equal. Thus, a p – n junction is formed.

V-I characteristics of a junction diode:
Forward characteristics:
It is the study of the variation in current through the diode with respect to the applied voltage across the diode when it is forward biased. An external resistance (R) is used to limit the flow of current through the diode. The voltage across the diode is varied by varying the biasing voltage across the dc power supply.

The forward bias voltage and the corresponding forward bias current are noted. A graph is plotted by taking the forward bias voltage (V) along the X – axis and the current (I) through the diode along the Y – axis. This graph is called the forward V-I characteristics of the p – n junction diode. Three inferences can be brought out from the graph:

(i) At room temperature, a potential difference equal to the barrier potential is required before a reasonable forward current starts flowing across the diode. This voltage is known as threshold voltage or cut-in voltage or knee voltage (V_th). It is approximately 0.3 V for Germanium and 0.7 V for Silicon. The current flow is negligible when the applied voltage is less than the threshold voltage. Beyond the threshold voltage, increase in current is significant even for a small increase in voltage.

(ii) The graph clearly infers that the current flow is not linear and is exponential. Hence it does not obey Ohm’s law.

(iii) The forward resistance (r_f) of the diode is the ratio of the small change in voltage (∆V)to the small change in current(∆I), r_f = \(\frac { ∆V }{ ∆I }\)

However, if the applied voltage is increased beyond a rated value, it will produce an extremely large current which may destroy the junction due to overheating. This is called as the breakdown of the diode and the voltage at which the diode breaks down is called the breakdown voltage. Thus, it is safe to operate a diode well within the threshold voltage and the breakdown voltage.

Reverse characteristics:
In the reverse bias, the p-region of the diode is connected to the negative terminal and n-region to the positive terminal of the dc power supply. A graph is drawn between the reverse bias voltage and the current across the junction, which is called the reverse characteristics of a p-n junction diode.

Under this bias, a very small current in μA, flows across the junction. This is due to the flow of the minority charge carriers called the leakage current or reverse saturation current. Besides, the current is almost independent of the voltage. The reverse bias voltage can be increased only up to the rated value otherwise the diode will enter into the breakdown region.

Question 3.
Draw the circuit diagram of a half wave rectifier and explain its working Half wave rectifier circuit:
Answer:
The half wave rectifier circuit. The circuit consists of a transformer, a p-n junction diode and a resistor. In a half wave rectifier circuit, either a positive half or the negative half of the AC input is passed through while the other half is blocked. Only one half of the input wave reaches the output. Therefore, it is called half wave rectifier. Here, a p-n junction diode acts as a rectifying diode.

During the positive half cycle:
When the positive half cycle of the ac input signal passes through the circuit, terminal A becomes positive with respect to terminal B. The diode is forward biased and hence it conducts. The current flows through the load resistor R_L and the AC voltage developed across R_L constitutes the output voltage V₀ and the waveform of the diode current.

During the negative half cycle:
When the negative half cycle of the ac input signal passes through the circuit, terminal A is negative with respect to terminal B. Now the diode is reverse biased and does not conduct and hence no current passes through R_L. The reverse saturation current in a diode is negligible. Since there is no voltage drop across R_L, the negative half cycle of ac supply is suppressed at the output.

The output of the half wave rectifier is not a steady dc voltage but a pulsating wave. This pulsating voltage is not sufficient for electronic equipments. A constant or a steady voltage is required which can be obtained with the help of filter circuits and voltage regulator circuits. Efficiency (η) is the ratio of the output dc power to the ac input power supplied to the circuit. Its value for half wave rectifier is 40.6 %.

Question 4.
Explain the construction and working of a full w ave rectifier.
Answer:
Full wave rectifier:
The positive and negative half cycles of the AC input signal pass through the full wave rectifier circuit and hence it is called the full wave rectifier. It consists of two p-n junction diodes, a center tapped transformer, and a load resistor (R_L). The centre is usually taken as the ground or zero voltage reference point. Due to the centre tap transformer, the output voltage rectified by each diode is only one half of the total secondary voltage.

During positive half cycle:
When the positive half cycle of the ac input signal passes through the circuit, terminal M is positive, G is at zero potential and N is at negative potential. This forward biases diode D₁ and reverse biases diode D₂. Hence, being forward biased, diode D₁ conducts and current flows along the path MD₁ AGC. As a resul t, positive half cycle of the voltage appears across R_L in the direction G to C.

During negative half cycle:
When the negative half cycle of the ac input signal passes through the circuit, terminal N is positive, G is at zero potential and M is at negative potential. This forward biases diode D₂ and reverse biases diode D₁. Hence, being forward biased, diode D₂ conducts and current flows along the path ND₂ BGC . As a result, negative half cycle of the voltage appears across R_L in the same direction from G to C.

Hence in a full wave rectifier both positive and negative half cycles of the input signal pass through the circuit in the same direction as shown in figure (b). Though both positive and negative half cycles of ac input are rectified, the output is still pulsating in nature. The efficiency (η) of full wave rectifier is twice that of a half wave rectifier and is found to be 81.2 %. It is because both the positive and negative half cycles of the ac input source are rectified.

Question 5.
What is an LED? Give the principle of operation with a diagram.
Answer:
Light Emitting Diode (LED):
LED is a p – n junction diode which emits visible or invisible light when it is forward biased. Since, electrical energy is converted into light energy, this process is also called electroluminescence. The cross-sectional view of a commercial LED is shown in figure (b). it consists of a p-layer, n-layer and a substrate. A transparent window is used to allow light to travel in the desired direction. An external resistance in series with the biasing source is required to limit the forward current through the LED. In addition, it has two leads; anode and cathode:

When the p – n junction is forward biased, the conduction band electrons on n-side and valence band holes on p-side diffuse across the junction. When they cross the junction, they become excess minority carriers (electrons in p-side and holes in n-side).

These excess minority carriers recombine with oppositely charged majority carriers in the respective regions, i.e. the electrons in the conduction band recombine with holes in the valence band as shown in the figure (c). During recombination process, energy is released in the form of light (radiative) or heat (non-radiative). For radiative recombination, a photon of energy hυ is emitted.

For non-radiative recombination, energy is liberated in the form of heat. The colour of the light is determined by the energy band gap of the material. Therefore, LEDs are available in a wide range of colours such as blue (SiC), green (AlGaP) and red (GaAsP). Now a days, LED which emits white light (GalnN) is also available.

Question 6.
Write notes on Photodiode?
Answer:
Photodiodes:
A p-n junction diode which converts an optical signal into electric current is known as photodiode. Thus, the operation of photodiode is exactly opposite to that of an LED. Photo diode words in reverse bias. Its circuit symbol is shown in figure (a). The direction of arrows indicates that the light is incident on the photo diode.

The device consists of a p – n junction semiconductor made of photosensitive material kept safely inside a plastic case. It has a small transparent window that allows light to be incident on the p – n junction. Photodiodes can generate current when the p – n junction is exposed to light and hence are called as light sensors.

When a photon of sufficient energy (hυ) strikes the depletion region of the diode, some of the valence band electrons are elevated into conduction band, in turn holes are developed in the valence band. This creates electron – hole pairs. The amount of electron – hole pairs generated depends on the intensity of light incident on the p-n junction. These electrons and holes are swept across the p-n junction by the electric field created by reverse voltage before recombination takes place. Thus, holes move towards the n-side and electrons towards the p-side.

When the external circuit is made, the electrons flow through the external circuit and constitute the photocurrent. When the incident light is zero, there exists a reverse current which is negligible. This reverse current in the absence of any incident light is called dark current and is due to the thermally generated minority carriers.

Question 7.
Explain the working principle of a solar cell. Mention its applications.
Answer:
Solar cell:
A solar cell, also known as photovoltaic cell, converts light energy directly into electricity or electric potential difference by photovoltaic effect. It is basically a p – n junction which generates emf when solar radiation falls on the p – n junction. A solar cell is of two types: p-type and n-type. Both types use a combination of p-type and n-type Silicon which together forms the p-n junction of the solar cell.

The difference is that p-type solar cells use p-type Silicon as the base with an ultra-thin layer of n-type Silicon as shown in Figure, while n-type solar cell uses the opposite combination. The other side of the p-Silicon is coated with metal which forms the back electrical contact. On top of the n-type Silicon, metal grid is deposited which acts as the front electrical contact. The top of the solar cell is coated with anti-reflection coating and toughened glass.

In a solar cell, electron-hole pairs are generated due to the absorption of light near the junction. Then the charge carriers are separated due to the electric field of the depletion region. Electrons move towards n-type Silicon and holes move towards p-type Silicon layer. The electrons reaching the n-side are collected by the front contact and holes reaching p-side are collected by the back electrical contact.

Thus a potential difference is developed across solar cell. When an external load is connected to the solar cell, photocurrent flows through the load. Many solar cells are connected together either in series or in parallel combination to form solar panel or module. Many solar panels are connected with each other to form solar arrays. For high power applications, solar panels and solar arrays are used.
Applications:

• Solar cells are widely used in calculators, watches, toys, portable power supplies, etc.
• Solar cells are used in satellites and space applications
• Solar panels are used to generate electricity.

Question 8.
Sketch the static characteristics of a common emitter transistor and bring out the essence of input and output characteristics.
Answer:
Static Characteristics of Transistor in Common Emitter Mode:
The know-how of certain parameters like the input resistance, output resistance, and current gain of a transistor are very important for the effective use of transistors in circuits. The circuit to study the static characteristics of an NPN transistor in the common emitter mode is given in figure.

The bias supply voltages V_BB and V_CC bias the base-emitter junction and collector- emitter junction respectively. The junction potential at the base-emitter is represented as V_BE and the collector-emitter as V_CE. The rheostats R₁ and R₂, are used to vary the base and collector currents respectively.
The static characteristics of the BJT are:

1. Input characteristics
2. Output characteristics
3. Transfer characteristics

1. Input Characteristics:
Input Characteristics curves give the relationship between the base current (I_B) and base to emitter voltage (V_BE) at constant collector to emitter voltage (V_CE) and are shown in figure. Initially, the collector to emitter voltage (V_CE) is set to a particular voltage (above 0.7 V to reverse bias the junction). Then the base-emitter voltage (V_BE) is increased in suitable steps and the corresponding base-current (I_B) is recorded. A graph is plotted with V_BE along the x-axis and I_B along the y-axis. The procedure is repeated for different values of V_CE.

The following observations are made from the graph:

1. The curve looks like the forward characteristics of an ordinary p-n junction diode.

2. There exists a threshold voltage or knee voltage (V_k) below which the base current is very small. The value is 0.7 V for Silicon and 0.3 V for Germanium transistors. Beyond the knee voltage, the base current increases with the increase in base-emitter voltage.

3. It is also noted that the increase in the collector-emitter voltage decreases the base current. This shifts the curve outward. This is because the increase in collector-emitter voltage increases the width of the depletion region in turn, reduces the effective base width and thereby the base current.

Input resistance:
The ratio of the change in base-emitter voltage (∆V_BE) to the change in base current (∆I_B) at a constant collector-emitter voltage (V_CE) is called the input resistance (R_i). The input resistance is not linear in the lower region of the curve.
R_i =\(\left(\frac{\Delta \mathrm{V}_{\mathrm{BE}}}{\Delta \mathrm{I}_{\mathrm{B}}}\right)_{\mathrm{V}_{\mathrm{CB}}}\)

The input resistance is high for a transistor in common emitter configuration. Output Characteristics:
The output characteristics give the relationship between the variation in the collector current (∆I_C) with respect to the variation in collector- emitter voltage (∆ V_CE) at constant input current (I_B) as shown in figure.

Initially, the base current (I_B) is set to a particular value. Then collector- emitter voltage (V_CE) is increased in suitable steps and the corresponding collector current (I_C) is recorded. A graph is plotted with the V_CE along the x-axis and I_C along the y-axis.

 

This procedure is repeated for different values of I_B, The four regions in are:
(i) Saturation region:
When V_CE is increased above 0 V, the Ic increases rapidly to a saturation value almost independent of I_B (Ohmic region, OA) called knee voltage. Transistors are always operated above this knee voltage.

(ii) Cut-off region:
A small collector current (I_C) exists even after the base current (I_B) is reduced to zero. This current is due to the presence of minority carriers across the collector-base junction and the surface leakage current (I_CEO). This region is called as the cut-off region, because the main collector current is cut-off.

(iii) Active region:
In this region, the emitter-base junction is forward biased and the collector-base junction is reverse biased. The transistor in this region can be used for voltage, current and power amplification.

(iv) Breakdown region:
If the collector-emitter voltage (V_CE) is increased beyond the rated value given by the manufacturer, the collector current (I_C) increases enormously leading to the junction breakdown of the transistor. This avalanche breakdown can damage the transistor.

Output Resistance:
The ratio of the change in the collector-emitter voltage (∆V_CE) to the corresponding change in the collector current (∆I_C) at constant base current (I_B ) is called output resistance (R_O).
R₀ =\(\left(\frac{\Delta \mathrm{V}_{\mathrm{CE}}}{\Delta \mathrm{I}_{\mathrm{C}}}\right)_{\mathrm{I}_{\mathrm{B}}}\)
The output resistance for transistor in common emitter configuration is very low.

Question 9.
Describe the function of a transistor as an amplifier with the neat circuit diagram. Sketch the input and output wave form.
Answer:
Transistor as an amplifier:
A transistor operating in the active region has the capability to amplify weak signals. Amplification is the process of increasing the signal strength (increase in the amplitude). If a large amplification is required, the transistors are cascaded with coupling elements like resistors, capacitors, and transformers which is called as multistage amplifiers.

Here, the amplification of an electrical signal is explained with a single stage transistor amplifier as shown in figure (a). Single stage indicates that the circuit consists of one transistor with the allied components. An NPN transistor is connected in the common emitter Configuration.

To start with, the Q point or the operating point of the transistor is fixed so as to get the maximum signal swing at the output (neither towards saturation point nor towards cut-off). A load resistance, R_C is connected in series with the collector circuit to measure the output voltage. The capacitor C₁ allows only the ac signal to pass through. The emitter bypass capacitor C_E provides a low reactance path to the amplified ac signal. The coupling capacitor C_C is used to couple one stage of the amplifier with the next stage while constructing multistage amplifiers. V_S is the sinusoidal input signal source applied across the base-emitter.
Collector currrent ,I_c = Iβ_B = [∴β=\(\frac { { I }_{ C } }{ { I }_{ B } } \)]
Applying Kirchhoff’s voltage law in the output loop, the collector-emitter voltage is given by
V_CE = V_CC – I_CR_C

Working of the amplifier:
1. During the positive half cycle:
Input signal (V_S) increases the forward voltage across the emitter-base. As a result, the base current (I_B) increases. Consequently, the collector current (I_C) increases β times. This increases the voltage drop across R_C which in turn decreases the collector-emitter voltage (V_CE). Therefore, the input signal in the positive direction produces an amplified signal in the negative direction at the output. Hence, the output signal is reversed by 180° as shown in figure (b).

2. During the negative half cycle:
Input signal (V_s ) decreases the forward voltage across the emitter-base. As a result, base current (I_B) decreases and in turn increases the collector current (I_C). The increase in collector current (I_C) decreases the potential drop across Rc and increases the collector-emitter voltage (V_CE). Thus, the input signal in the negative direction produces an amplified signal in the positive direction at the output. Therefore, 180° phase reversal is observed during the negative half cycle of the input signal.

Question 10.
Transistor functions as a switch. Explain.
Answer:
The transistor in saturation and cut – off regions functions like an electronic switch that helps to turn ON or OFF a given circuit by a small control signal.

1. Presence of dc source at the input (saturation region):
When a high input voltage (V_in = +5V) is applied, the base current (I_B) increases and in turn increases the collector current. The transistor will move into the saturation region (turned ON). The increase in collector current (I_C) increases the voltage drop across Rc, thereby lowering the output voltage, close to zero. The transistor acts like a closed switch and is equivalent to ON condition.

2. Absence of dc source at the input (cut-off region):
A low input voltage (V_in = 0V), decreases the base current (I_B) and in turn decreases the collector current (I_c). The transistor will move into the cut-off region (turned OFF). The decrease in collector current (Ic) decreases the drop across Rc, thereby increasing the output voltage, close to +5 V.

The transistor acts as an open switch which is considered as the OFF condition. It is manifested that, a high input gives a low output and a low input gives a high output. In addition, we can say that the output voltage is opposite to the applied input voltage. Therefore, a transistor can be used as an inverter in computer logic circuitry.

Question 11.
State Boolean laws. Elucidate how they are used to simplify Boolean expressions with suitable example.
Answer:
Law’s of Boolean Algebra: The NOT, OR and AND operations are \(\overline { A } \), A + B, A . B are the Boolean operations. The results of these operations can be summarised as:
Complement law

The complement law can be realised as
OR laws:

AND laws:

The Boolean operations obey the following laws.
Commutative laws
A+ B = B + A
A. B = B . A
Associative laws
A + (B + C) = (A + B) + C
A . (B . C) = (A .B) . C
Distributive laws
A( B + C) = AB + AC
A + BC = (A + B) (A + C)
The above laws are used to simplify complicated expressions and to simplify the logic circuitry.

Question 12.
State and prove De Morgan’s First and Second theorems.
Answer:
De Morgan’s First Theorem:
The first theorem states that the complement of the sum of two logical inputs is equal to the product of its complements.
Proof:
The Boolean equation for NOR gate is Y = \(\overline { A+B } \). The Boolean equation for a bubbled AND gate is Y = \(\overline { A } \). \(\overline { B } \) . Both cases generate same outputs for same inputs. It can be verified using the following truth table.

From the above truth table, we can conclude \(\overline { A+B } \) = \(\overline { A } \). \(\overline { B } \) . Thus De Morgan’s First Theorem is proved. It also says that a NOR gate is equal to a bubbled AND gate. The corresponding logic circuit diagram is shown in figure.

De Morgan’s Second Theorem:
The second theorem states that the complement of the product of two inputs is equal to the sum of its complements.
Proof:
The Boolean equation for NAND gate is Y = \(\overline { AB } \)
The Boolean equation for bubbled OR gate is Y = \(\overline { A } \) + \(\overline { B } \) . A and B are the inputs and Y is the output. The above two equations produces the same output for the same inputs. It can be verified by using the truth table.

From the above truth table we can conclude \(\overline { A.B } \) = \(\overline { A } \) + \(\overline { B } \). Thus De Morgan’s Second Theorem is proved. It also says, a NAND gate is equal to a bubbled OR gate. The corresponding logic circuit diagram is shown in figure.

Samacheer Kalvi 12th Physics Semiconductor Electronics Numerical Problems

Question 1.
The given circuit has two ideal diodes connected as shown in figure below. Calculate the current flowing through the resistance R₁.
Answer:
Diode D₁ is reverse biased so, it will block the current and Diode D₂ is forward biased, so it will pass the current.
Current in the circuit is
I = \(\frac { V }{ { R }_{ s } } \) = \(\frac { 10 }{ 2+2 }\) = \(\frac { 10 }{ 4 }\) = 2.5 a
I = 2.5 A

Question 2.
Four silicon diodes and a 10 resistor are connected as shown in figure below. Each diode has a resistance of 1Ω Find the current flows through the 18Ω resistor.
Answer:
Diodes D₂ and D₄ are forward biased while diodes D₁ and D₃ are reverse biased. Only current flowing through the closed loop is EADCBFE. Consider the applied voltage is 4V. For silicon diode, Barrier Voltage is 0.7V.

Net circuit Voltages = 4 – (0.7 + 0.7) = 4 1.4
V = 2.6 V
Total circuit resistance = 1 + 18 + 1
R = 20 Ω
∴ Circuit Current I = \(\frac { V }{ R }\) = \(\frac { 2.6 }{ 20 }\)

Question 3.
Assuming V_CEsat = 0.2 V and β = 50, find the minimum base current (I_B) required to drive the transistor given in the figure to saturation.
Solution:

Question 4.
A transistor having α =0.99 and V_BE = 0.7V, is given in the circuit. Find the value of the collector current.
Solution:

Question 5.
In the circuit shown in the figure, the BJT has a current gain (β) of 50. For an emitter – base voltage V_EB = 600 mV, calculate the emitter – collector voltage V_EC (in volts).
Solution:

Samacheer Kalvi 12th Physics Semiconductor Electronics Additional Questions

Samacheer Kalvi 12th Physics Semiconductor Electronics Multiple Choice Questions

Question 1.
The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature
(a) increase exponentially with increasing band gap
(b) decrease exponentially with increasing band gap
(c) decreases with increasing temperature
(d) is independent of the temperature and the band gap.
Answer:
(b) decrease exponentially with increasing band gap
Hint:
At a finite temperature, the probability of jumping an electron from valence band to conduction band decreases exponentially with the increasing band gap (E_g )
n = n₀ e^-E_g/k_BT

Question 2.
The electrical conductivity of a semiconductor increase when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it. The band gap (in eV) for the semiconductor is-
(a) 0.9
(b) 0.7
(c) 0.5
(d) 1.1.
Answer:
(c) 0.5
Hint:

Question 3.
Which of the following statements is not true?
(a) The resistance of intrinsic semiconductor decreases with increase of temperature.
(b) Doping pure Si with trivalent impurities gives p-type semiconductors.
(c) The majority carriers in n-type semiconductors and holes
(d) Ap-n junction can act as a semiconductor diode.
Answer:
(c) The majority carriers in n-type semiconductors and holes
Hint:
The majority charge carriers in n-type semiconductors are electrons not holes. Only option (c) is not true.

Question 4.
Holes are charge carrier in
(a) intrinsic semiconductors
(b) ionic solids
(c) p-type semiconductor
(d) metals.
Answer:
(a) intrinsic semiconductors
Hint:
(a) In intrinsic semiconductor, n_h = n_e
(b) In P-type semiconductor, n_h >> n_e

Question 5.
A transistor is used in the common emitter mode as an amplifier. Then
(a) the base – emitter junction is forward – biased
(b) the base – emitter junction is reverse – biased
(c) the input signal is connected in series with the voltage applied to bias the base – emitter junction
(d) the input signal is connected in series with the voltage applied to bias the base – collector junction.
Answer:
(c) the input signal is connected in series with the voltage applied to bias the base – emitter junction
Hint:
In CE – transistor amplifier, the base – emitter junction is forward bias and the input signal is connected in series with the base – emitter battery.

Question 6.
The energy band gap is maximum in-
(a) metals
(b) superconductors
(c) insulators
(d) semiconductors.
Answer:
(c) insulators
Hint:
The band gap is maximum in insulators.

Question 7.
At absolute zero, Si acts as-
(a) non – metal
(b) metal
(c) insulator
(d) none of these.
Answer:
(c) insulator
Hint:
At absolute zero, Si acts as an insulator due to the absence of free electrons in the conduction band.

Question 8.
Apiece of copper and another of germanium are cooled from room temperature to 77 K. The resistance of
(a) each of these decreases
(b) copper strip increases and that of germanium decreases
(c) copper strip decreases and that of germanium increases
(d) each of these increases.
Answer:
(c) copper strip decreases and that of germanium increases
Hint:
With the decrease of temperature, the resistance of copper (a metallic conductor) decreased while that of germanium (a semiconductor) increases.

Question 9.
In the middle of the depletion layer of reverse biased p – n junction, the-
(a) electric field is zero
(b) potential is zero
(c) potential is maximum
(d) electric field is maximum.
Answer:
(a) electric field is zero
Hint:
When a p – n junction is reverse biased, the width of the depletion layer becomes large and so the electric field (E = v/d) becomes very small, nearly zero.

Question 10.
In a full wave rectifier circuit operating from 50 Hz mains, frequency, the fundamental frequency in the ripple would be-
(a) 50 Hz
(b) 25 Hz
(c) 100 Hz
(d) 70.7 Hz.
Answer:
(c) 100 Hz
Hint:
The frequency of the ripple in the output of a fullwave rectifier is twice the frequency of the a.c. input. Hence, it is 100 Hz.

Question 11.
The part of a transistor, which is heavily doped to produce a large number of majority carriers is called?
(a) emitter
(b) base
(c) collector
(d) any one out of emitter, base and collector.
Answer:
(a) emitter
Hint:
Emitter of a transistor is heavily doped so as to act as source of majority charge carriers.

Question 12.
When n – p – n transistor is used as an amplifier, then-
(a) electrons move from base to collector
(b) holes move from emitter to base
(c) electrons move from collector to base
(d) holes move from base to emitter.
Answer:
(a) electrons move from base to collector
Hint:
When n – p – n transistor is in operation, the majority charge carriers, i.e., electrons move from emitter to base and then to collector.

Question 13.
In a common – base amplifier, the phase difference between the input signal voltage and the output voltage (across collector and base) is
(a) 0
(b) π/4
(c) π/2
(d) π.
Answer:
(a) 0
Hint:
In a common – base amplifier, the input and output voltages are in the same phase.

Question 14.
In a common – base mode of a transistor, the collector current is 5.488 mA for an emitter current of 5.60 A. The value of the base current amplification factor (β) will be-
(a) 49
(b) 50
(c) 51
(d) 48.
Answer:
(a) 49
Hint:
β = \(\frac { { I }_{ C } }{ { I }_{ B } } \) = \(\frac { 5.488 }{ 0.112 }\) = 49.

Question 15.
In the circuit below, A and B represent two inputs and C represents the output. The circuit represents

(a) OR gate
(b) NOR gate
(c) AND gate
(d) NAND gate.
Answer:
(a) OR gate
Hint:
The given circuit represents an OR gate, when either A or B or both inputs are high, the output C is high.

Question 16.
In a fee lattice structure, what is the effective number of atoms?
(a) 4
(b) 3
(c) 2
(d) 1.
Answer:
(a) 4
Hint:
N = \(\frac { { N }_{ C } }{ 8 } \) + \(\frac { { N }_{ F } }{ 2 } \) = \(\frac { 8 }{ 8 }\) + \(\frac { 6 }{ 2 }\) = 4.

Question 17.
Monoclinic crystal lattice has dimensions-
(a) α = β = γ
(b) α = β = 90°, γ ≠ 90°
(e) α ≠ β ≠ γ
(d) none of these.
Answer:
(b) α = β = 90°, γ ≠ 90°
Hint:
For a monoclinic crystal, α ≠ β ≠ c and α = β = 90°≠ γ.

Question 18.
In insulators?
(a) valence band is partially filled
(b) conduction band is partially filled with electrons
(c) conduction band is filled with electrons and valence band is empty
(d) conduction band is empty and valence band is completely filled with electrons.
Answer:
(d) conduction band is empty and valence band is completely filled with electrons.
Hint:
In insulators, the conduction band is empty and valence band is completely filled with electrons.

Question 19.
The valence band and conduction band of a solid overlap at low temperature, the solid may be-
(a) a metal
(b) a semiconductor
(c) an insulator
(d) none of these.
Answer:
(a) a metal
Hint:
In metals, the valence band and conduction band may overlap at low temperature.

Question 20.
If germanium is dopped with arsenic, that will result in-
(a) n-type semiconductor
(b) p-type semiconductor
(c) intrinsic semiconductor
(d) none of these.
Answer:
(a) n-type semiconductor
Hint:
Arsenic is pentavalent. Its doping with germanium results in n-type semiconductor.

Question 21.
n-type semiconductor is
(a) positive charged
(b) negatively charged
(c) neutral
(d) positive or negative depending upon doping material.
Answer:
(c) neutral
Hint:
Semiconductors maintain their electrical neutrality even after doping.

Question 22.
To a germanium ciystal equal number of aluminium and indium atoms are added. Then
(a) it remains an intrinsic semiconductor
(b) it becomes an n-type semiconductor
(c) it becomes a p-type semiconductor
(d) it becomes an insulator.
Answer:
(c) it becomes a p-type semiconductor
Hint:
Both A1 and In are trivalent atoms. Their doping in germanium results in a p-type semiconductor.

Question 23.
The dominant contribution to current comes from holes in case of-
(a) metals
(b) intrinsic semiconductors
(c) p-type extrinsic semiconductors
(d) n-type extrinsic semiconductors.
Answer:
(c) p-type extrinsic semiconductors
Hint:
Holes are the majority charge carriers in p-type extrinsic semiconductors.

Question 24.
For a heavily doped n-type semiconductor, fermi – level lies-
(a) a little below the conduction band
(b) a little above the valence band
(c) a little inside the valence band
(d) at the centre of the band gap.
Answer:
(a) a little below the conduction band
Hint:
For a heavily doped n-type semiconductor, the fermi level lies slightly below the bottom of the conduction band.

Question 25.
The coordination number for a bcc crystal is-
(a) 4
(b) 8
(c) 12
(d) 6.
Answer:
(b) 8
Hint:
The eight comer atoms of the unit cell are close neighbourers of the atom at the body centre.

Question 26.
If the forward voltage in a diode is increased the width of the depletion region-
(a) increases
(b) decreases
(c) fluctuates
(d) no change.
Answer:
(b) decreases
Hint:
If the forward voltage in a diode is increased, the width of depletion region decreases.

Question 27.
In order to rectify an alternating current one uses a-
(a) thermocouple
(b) diode
(c) triode
(d) transistor.
Answer:
(b) diode
Hint:
A diode is used to rectify an alternating current.

Question 28.
Why is there sudden increase in current in zener diode?
(a) due to rupture of bonds
(b) resistance of depletion layer becomes less
(c) due to high doping
(d) none of the above.
Answer:
(a) due to rupture of bonds
Hint:
The sudden increase in current in a zener diode is due to the rupture of many covalent bonds.

Question 29.
In a transistor
(a) there is 1 p – n junction
(b) there are 2 p – n junction
(c) there are 3 p – n junction
(d) none of the above.
Answer:
(b) there are 2 p – n junction
Hint:
A transistor is like a combination of two p-n junctions placed back to back.

Question 30.
Let i_e, i_c and i_b represent emitter current, collector current and the base current of a transistor, then
(a) i_c > i_e
(b) i_b > i_c
(c) i_b < i_c
(d) i_e > i_c
Answer:
(d) i_e > i_c
Hint:
As i_e = i_c + i_b
∴ i_i >_c

Question 31.
In common – emitter amplifier the ratio \(\frac { { I }_{ C } }{ { I }_{ E } } \) is 0.98. The current gain will be
(a) 4.9
(b) 7.8
(c) 49
(d) 78.
Answer:
(c) 49
Hint:
\(\frac { α }{ 1-α } \) = \(\frac { 0.98 }{ 1-0.98 } \) = \(\frac { 0.98 }{ 0.02 } \) = 49

Question 32.
The gate for which output is high, if atleast one input is low?
(a) NAND
(b) NOR
(c) AND
(d) OR.
Answer:
(a) NAND
Hint:
The output of a NAND gate is high, if atleast one input is low.

Question 33.
An oscillator is nothing but an amplifier with-
(a) positive feedback
(b) large gain
(c) no feedback
(d) negative feedback.
Answer:
(a) positive feedback
Hint:
When a transistor is used as an amplifier with positive feedback, it works as an oscillator.

Question 34.
Crystalline solid are?
(a) anisotropic
(b) isotropic
(c) amporphus
(d) none of these.
Answer:
(a) anisotropic
Hint:
Crystalline solids are anisotropic as they show different physical properties along different directions.

Question 35.
Which of the following is an amorphous solid?
(a) Glass
(b) Diamond
(c) Salt
(d) Sugar.
Answer:
(a) Glass

Question 36.
Energy required to break one band in DNA is
(a) ≈ 1 eV
(b) ≈ 0.1 eV
(c) ≈ 0.01 eV
(d) ≈ 2.1 eV.
Answer:
(a) ≈ 1 eV
Hint:
The bond strength in DNA is nearly 1 eV.

Question 37.
An intrinsic semiconductor, at the absolute zero temperature, behaves like a/an?
(a) insulator
(b) superconductor
(c) n-type semiconductor
(d) p-type semiconductor.
Answer:
(a) insulator
Hint:
At the absolute zero temperature, an intrinsic semiconductor behaves like an insulator.

Question 38.
In a semiconducting material the mobilities of electrons and holes are µ_e and µ_h respectively. Which of the following is true?
(a) µ_e > µ_h
(b)µ_e < µ_h
(c) µ_e = µ_h
(d)µ_e < 0 ; µ_h > 0.
Answer:
(a) µ_e > µ_h
Hint:
The mobility of an electron in the conduction is more than the mobility of a hole in the valence band.

Question 39.
In a pure semiconductor crystal, if current flows due to breakage of crystal bonds, then the semiconductor is called
(a) acceptor
(b) donor
(c) intrinsic semiconductor
(d) extrinsic semiconductor.
Answer:
(c) intrinsic semiconductor
Hint:
Pure semiconductors are called intrinsic semiconductors.

Question 40.
Which of the following, when added as an impurity into the silicon, produces n-type semiconductor?
(a) phosphorous
(b) aluminium
(c) magnesium
(d) both (b) and (c).
Answer:
(a) phosphorous
Hint:
As phosphorous is pentavalent, it produces n-type semiconductor when added to silicon.

Question 41.
In n-type semiconductors, majority charge carriers are
(a) holes
(b) protons
(c) neutrons
(d) electrons.
Answer:
(d) electrons

Question 42.
In p-type semiconductor,
(a) major current carrier are electrons
(b) major carrier are mobile negative ions
(c) major carrier are mobile holes
(d) the number of mobile holes exceeds the number of acceptor atoms.
Answer:
(c) major carrier are mobile holes
Hint:
In p-type semiconductors, holes are the majority charge carriers.

Question 43.
The potential barrier in the depletion layer is due to-
(a) ions
(b) holes
(c) electrons
(d) forbidden band.
Answer:
(a) ions
Hint:
The potential barrier in the depletion layer is due to the presence of immobile ions.

Question 44.
When a p-n diode is reverse biased, then
(a) no current flows
(b) the depletion region is increased
(c) the depletion region is reduced
(d) the height of the potential barrier is reduced.
Answer:
(b) the depletion region is increased
Hint:
When a p-n junction is reverse biased, its depletion region is widened.

Question 45.
If a p-n diode is reverse biased, then the resistance measured by an ohm meter, will be
(a) zero
(b) low
(c) high
(d) infinite.
Answer:
(c) high
Hint:
When a p-n diode is reverse biased, it offers a high resistance.

Question 46.
Diode is used as an/a?
(a) oscillator
(b) amplifier
(c) rectifier
(d) modulator.
Answer:
(c) rectifier

Question 47.
In the half wave rectifier circuit operating from 50 Hz main frequency, the fundamental frequency in the ripple would be-
(a) 25 Hz
(b) 50 Hz
(c) 70.7 Hz
(d) 100 Hz
Answer:
(b) 50 Hz.
Hint:
In a half wave rectifier, fundamental frequency in the ripple = Input frequency = 50 Hz.

Question 48.
Zener diode acts as a/an?
(a) oscillator
(b) regulator
(c) rectifier
(d) filter.
Answer:
(b) regulator

Question 49.
A transistor is a/an?
(a) chip
(b) insulator
(c) semiconductor
(d) metal.
Answer:
(c) semiconductor

Question 50.
The minimum potential difference between the base and emitter required to switch a silicon transistor ON is approximately.
(a) IV
(b) 3V
(c) 5V
(d) 4.2 V.
Answer:
(a) IV
Hint:
For switching on a silicon transistor, (V_BE)_min ≈ 1V.

Question 51.
When n-p-n transistor is used as an amplifier, then
(a) holes moves from emitter
(b) electrons move from base to collector
(c) holes move from base to emitter
(d) electrons move from collector to base.
Answer:
(b) electrons move from base to collector

Question 52.
The current gain for a transistor working as common base amplifier is 0.96. If the emitter current is 7.2 mA, then the base current is-
(a) 0.29 mA
(b) 0.35 mA
(c) 0.39 mA
(d) 0.43 mA.
Answer:
(a) 0.29 mA
Hint:
α = \(\frac { { I }_{ C } }{ { I }_{ E } } \) (or) 0.96 = \(\frac { { I }_{ C } }{ 7.2mA} \)
I_C = 0.96 x 7.2 = 6.91 mA
I_B = I_C – I_E = 7.2 – 6.91 =0.29 mA.

Question 53.
Consider an n-p-n transistor amplifier in common – emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?
(a) 1.1 mA
(b) 1.01 mA
(c) 0.01 mA
(d) 10 mA.
Answer:
(b) 1.01 mA
Hint:
β = \(\frac { { \triangle I }_{ C } }{ { \triangle I }_{ E } } \) ∴ ∆I_B = \(\frac { { \triangle I }_{ C } }{ β } \) = \(\frac { 1mA }{ β }\) = 0.01 mA
∆I_E= ∆I_B + ∆I_C = 0.01 + 1 = 1.01 mA.

Question 54.
An amplifier has voltage gain = 1000. The voltage gain (in dB) is-
(a) 30 dB
(b) 60 dB
(c) 3 dB
(d) 20 dB.
Answer:
(b) 60 dB
Hint:
Voltage gain in dB = 20 log₁₀ A_v= 20 log₁₀ (1000) = 20 x 3 = 60 dB.

Question 55.
Boolean algebra is essentially based on-
(a) logic
(b) truth
(c) numbers
(d) symbol.
Answer:
(a) logic

Question 56.
The number (0) zero is required for-
(a) transistor
(b) abacus
(c) computer
(d) calculator.
Answer:
(c) computer
Hint:
A computer work on binary digits 0 and 1.

Question 57.
Which of the following logic gates in a universal gate?
(a) OR
(b) NOT
(c) AND
(d) NAND.
Answer:
(d) NAND.
Hint:
NAND gate is a universal gate because its repeated use can give all basic gates like OR, AND and NOT gates.

Question 58.
Which of the following is the weakest kind of the bonding in solids?
(a) Ionic
(b) Metallic
(c) Van der waals
(d) Covalent.
Answer:
(c) Van der waals

Question 59.
The cations and anions are arranged in alternate form in-
(a) metallic crystal
(b) ionic crystal semi – conductor
(c) covalent crystal
(d) crystal.
Answer:
(b) ionic crystal semi – conductor

Question 60.
Diamond is very hard because-
(a) it is covalent solid
(b) it has large cohesive energy
(c) high melting point
(d) insoluble in all solvents.
Answer:
(b) it has large cohesive energy

Question 61.
Number of atoms per unit cell in bcc lattice is-
(a) 9
(b) 4
(c) 2
(d) 1.
Answer:
(c) 2
Hint:
N = N_B + \(\frac { { N }_{ C } }{ 8 } \) = 1 + \(\frac { 8 }{ 8 }\) = 2.

Question 62.
At absolute zero, Si acts as?
(a) non metal
(b) metal
(c) 2
(d) 1.
Answer:
(c) 2
Hint:
At absolute zero, Si acts as an insulator because it has no free electrons in the conduction band.

Question 63.
Which of the following, when added as an impurity into the silicon produces n-type semi – conductor?
(a) B
(b) AL
(c) P
(d) Mg.
Answer:
(c) P
Hint:
Only P is a pentavalent impurity atom,its doping with germanium produces a p-types semi – conductor.

Question 64.
To obtain a p-type germanium semiconductor, it must be doped with-
(a) indium
(b) phosphorus
(c) arsenic
(d) antimony.
Answer:
(a) indium
Hint:
Only In is a trivalent impurity atom, its doping with germanium produces a p-type semi-conductor.

Question 65.
When arsenic is added as an impurity to silicon, the resulting material is-
(a) n-type conductor
(b) n-type semiconductor
(c) P – type semiconductor
(d) none of these.
Answer:
(b) n-type semiconductor
Hint:
When pentavalent arsenic is doped to silicon, it forms n-type semi – conductor.

Question 66.
In a p-type semiconductor, the majority carriers of current are-
(a) protons
(b) electrons
(c) holes
(d) neutrons.
Answer:
(c) holes

Question 67.
The depletion layer in the p – n junction region is caused by-
(a) drift of holes
(b) diffusion of charge carriers
(c) migration of impurity ions
(d) drift of electrons.
Answer:
(b) diffusion of charge carriers
Hint:
The depletion layer in the p-n junction region is caused by diffusion of charge carriers.

Question 68.
In the depletion region of an unbiased p – n junction diode, there are-
(a) holes
(b) mobile ions
(c) electrons
(d) immobile ions.
Answer:
(d) immobile ions.
Hint:
The depletion layer consists of immobile ions.

Question 69.
In forward bias, the width of potential barrier in a p – n junction adiode.
(a) remain constant
(b) decreases
(c) increases
(d) first (a) then (b).
Answer:
(b) decreases

Question 70.
Reverse bias applied to a junction diode-
(a) lowers the potential barrier
(b) raises the potential barrier
(c) increases the majority carrier current
(d) increases the minority carrier current.
Answer:
(b) raises the potential barrier

Question 71.
Barrier potential of a p – n junction diode does not depend on-
(a) diode design
(b) temperature
(c) forward bias
(d) doping density.
Answer:
(a) diode design
Hint:
Barrier potential depends upon temperature, doping density and forward biasing.

Question 72.
The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The d.c component of the output voltage is-
(a) \(\frac { 10 }{ \sqrt { 2V } } \)
(b) \(\frac { 10 }{ πV }\)
(c) 10v
(d) \(\frac { 20 }{ πV }\).
Answer:
(b) \(\frac { 10 }{ πV }\)
Hint:
V_dc = V_m = \(\frac { { V }_{ 0 } }{ π } \) = \(\frac { 10 }{ π }\) V.

Question 73.
A p-n junction diode can be used as-
(a) condenser
(b) regulator
(c) amplifier
(d) rectifier.
Answer:
(d) rectifier.

Question 74.
Zener diode is used for-
(a) amplification
(b) rectification
(c) stabilisation
(d) producing oscillations in an oscillator.
Answer:
(d) producing oscillations in an oscillator.
Hint:
Zener diode can be used for stabilisation of voltage.

Question 75.
When n-p-n transistor is used as an amplifier, then
(a) electrons move from collector to base
(b) holes move from base to emitter
(c) electrons move from base to collector
(d) electrons move from emitter to base
Answer:
(c) electrons move from base to collector
Hint:
When n-p-n transistor is used an amplifier, the majority carrier electrons move from base to collector.

Question 76.
The correct relationship between the two current gains a and P in a transistor is-
(a) α = \(\frac { β }{ 1+β }\)
(b) α = \(\frac { 1+β }{ β }\)
(c) β = \(\frac { α }{ 1+α }\)
(d) β = \(\frac { α }{ α-1 }\).
Answer:
(a) α = \(\frac { β }{ 1+β }\)
Hint:
β = \(\frac { α }{ 1+α }\) (or) β – βα = α ; α = \(\frac { β }{ 1+β }\).

Question 77.
The correct relation for a, P for a transistor is-
(a) β = \(\frac { 1-α }{ α }\)
(b) β = \(\frac { α }{ 1-α }\)
(c) α = \(\frac { β-1 }{ β }\)
(d) αβ = 1.
Answer:
(b) β = \(\frac { α }{ 1-α }\)

Question 78.
For a common base circuit if \(\frac {{ I }_{C}}{ { I }_{E} }\) = 0.98, then current gain for common emitter circuit will be-
(a) 49
(b) 98
(c) 4.9
(d) 25.5.
Answer:
(a) 49
Hint:
Here \(\frac {{ I }_{C}}{ { I }_{E} }\) = α = 0.98 ; β = \(\frac { α }{ 1-α }\) = \(\frac { 0.98 }{ 1-0.98 }\) = 49.

Question 79.
Radio waves of constant amplitude can be generated with-
(a) FET
(b) filter
(c) rectifier
(d) oscillator.
Answer:
(d) oscillator.

Question 80.
An oscillator is an amplifier with-
(a) a large gain
(b) negative feedback
(c) positive feedback
(d) no feedback.
Answer:
(c) positive feedback

Question 81.
The output of OR gate is 1
(a) if both inputs are zero
(b) if either or both inputs are 1
(c) only if both inputs are 1
(d) if either input is zero.
Answer:
(b) if either or both inputs are 1

Question 82.
The device that can act as a complete electronic circuit is-
(a) junction diode
(b) integrated circuit
(c) junction transistor
(d) zener diode.
Answer:
(b) integrated circuit

Question 83.
At absolute zero temperature, a semiconductor acts as a/an.
(a) dielectric
(b) conductor
(c) insulator
(d) none of these.
Answer:
(c) insulator

Question 84.
At which temperature, a pure semiconductor behave slightly as a conductor?
(a) low temperature
(b) room temperature
(c) high temperature
(d) both (a) and (b).
Answer:
(b) room temperature

Question 85.
In germanium crystal, the forbidden energy gap in joule is.
(a) 1.6 x 10^-19
(b) zero
(c) 1.12 x 10^-19
(d) 1.76 x 10^-19
Answer:
(c) 1.12 x 10^-19
Hint:
For a germanium crystal,
E_g = 0.7 eV = 0.7 x 1.6 x 10^-19 J = 1.12 x 10^-19 J.

Question 86.
In a p-type semiconductor, germanium is doped with.
(a) gallium
(b) boron
(c) aluminium
(d) all of these
Answer:
(d) all of these
Hint:
Ga, B and A1 are all trivalent atoms, they produce p-type semiconductor.

Question 87.
The major carrier of current in a p-type semiconductor will be.
(a) neutrons
(b) protons
(c) electrons
(d) holes.
Answer:
(d) holes.
Hint:
Holes are the major carriers of current in a p-type semiconductor.

Question 88.
Rectification is the process of conversion of
(a) a.c into d.c
(b) low a.c into high a.c
(c) d.c into a.c
(d) low d.c into high d.c
Answer:
(a) a.c into d.c

Question 89.
Which type of gate is represented by the given figure?

(a) NAND
(b) NOT
(c) AND
(d) OR.
Answer:
(b) NOT
Hint:
When both the inputs of a NAND gate are joined, it functions as a NOT gate.

Question 90.
Which of the following gates can be served as a building block for any digital circuit?
(a) OR
(b) NOT
(c) AND
(d) NAND.
Answer:
(d) NAND.
Hint:
A NAND gate is a universal gate.

Samacheer Kalvi 12th Physics Semiconductor Electronics Short Answer Questions

Question 1.
What are passive and active components.
Answer:
Passive components:
Components that cannot generate power in a circuit.
Active components:
components that can generate power in a circuit.

Question 2.
What are energy band?
Answer:
The band of very large number of closely spaced energy levels in a very small energy range is known as energy band.

Question 3.
What are valence band, conduction band and forbidden energy gap.
Answer:
The energy band formed due to the valence orbitals is called valence band and that formed due to the unoccupied orbitals is called the conduction band. The energy gap between the valence band and the conduction band is called forbidden energy gap.

Question 4.
What are intrinsic semiconductor?
Answer:
A semiconductor in its pure form without impurity is called an intrinsic semiconductor. In intrinsic semiconductors, the number of electrons in the conduction band is equal to the number of holes in the valence band.

Question 5.
What are extrinsic semiconductor?
Answer:
An extrinsic semiconductor is a semiconductor doped by a specific impurity which is able to deeply modify its electrical properties, making it suitable for electronic applications (diodes, transistors etc.) or optoelectronic applications (light emitters and detectors).

Question 6.
What are holes?
Answer:
The vacancy or absense of an electron in the bond of a covalently bonded crystal is called a hole.

Question 7.
What is meant by biasing and bias voltage?
Answer:
Biasing means providing external energy to charge carriers to overcome the barrier potential and make them move in a particular direction. The external voltage applied to the p-n junction is called bias voltage.

Question 8.
What are called forward bias and reverse bias?
Answer:

• If the positive terminal of the external voltage source is connected to the p-side and the negative terminal to the n-side, it is called forward bias.
• If the positive terminal of the battery is connected to the n-side and the negative potential to the p-side, the junction is said to be reverse biased.

Question 9.
Define knee voltage or threshold voltage or cut-in voltage.
Answer:
At room temperature, a potential difference equal to the barrier potential is required before a reasonable forward current starts flowing across the diode. This voltage is known as threshold voltage or cut-in voltage or knee voltage (V_th).

Question 10.
What is a Rectification?
Answer:
Rectification is the process of converting alternating current into direct current is called rectification.

Question 11.
Define – Efficiency of rectifier.
Answer:
Efficiency (η) is the ratio of the output dc power to the ac input power supplied to the circuit.

Question 12.
What is meant by zener effect?
Answer:
The electric field is strong enough to break or rupture the covalent bonds in the lattice and thereby generating electron-hole pairs. This effect is called Zener effect.

Question 13.
What is a zener diode?
Answer:
A junction diode specially designed to operate only in the reverse breakdown region continuously (without getting damaged) is called a zener diode.

Question 14.
Write down the applications of zener diode.
Answer:
The zener diode can be used as:

1. Voltage regulators
2. Peak clippers
3. Calibrating voltages
4. Provide fixed reference voltage in a network for biasing
5. Meter protection against damage from accidental application of excessive voltage.

Question 15.
What is peak inverse voltage (PIV)?
Answer:
The maximum reverse bias that can be applied before entering into the Zener region is called the Peak inverse voltage.

Question 16.
What is Optoelectronic devices?
Answer:
Optoelectronics deals with devices which convert electrical energy into light and light into electrical energy through semiconductors.

Question 17.
Write down the applications of LED’s?
Answer:

• Indicator lamps on the front panel of the scientific and laboratory equipments.
• Seven-segment displays.
• Traffic signals, exit signs, emergency vehicle lighting etc.
• Industrial process control, position encoders, bar graph readers.

Question 18.
Write down the applications of photodiodes?
Answer:

• Alarm system
• Count items on a conveyer belt
• Photoconductors
• Compact disc players, smoke detectors
• Medical applications such as detectors for computed tomography etc.

Question 19.
Write down the applications of solar cell.
Answer:

• Solar cells are widely used in calculators, watches, toys, portable power supplies, etc.
• Solar cells are used in satellites and space applications
• Solar panels are used to generate electricity.

Question 20.
What is a solar cell.
Answer:
A solar cell, also known as photovoltaic cell, converts light energy directly into electricity or electric potential difference by photovoltaic effect.

Question 21.
Write down the applications of Oscillators.
Answer:
Applications of oscillators:

• to generate a periodic sinusoidal or non sinusoidal wave forms.
• to generate RF carriers.
• to generate audio tones
• to generate clock signal in digital circuits.
• as sweep circuits in TV sets and CRO.

Question 22.
Write down concept of Barkhausen conditions for sustained oscillations.
Answer:
Barkhausen conditions for sustained oscillations
The following condition called Barkhausen conditions should be satisfied for sustained oscillations in the oscillator.

• The loop phase shift must be 0° or integral multiples of 2π.
• The loop gain must be unity. |Aβ| = 1
  Here; A → Voltage gain of the amplifier,
  b → feedback ratio; (fraction of the output that is fed back to the input)

Samacheer Kalvi 12th Physics Semiconductor Electronics Long Answer Questions

Question 1.
Explain the classification of materials.
Answer:
Insulators:
The valence band and the conduction band are separated by a large energy gap. The forbidden energy gap is approximately 6 eV in insulators. The gap is very large that electrons from valence band cannot move into conduction band even on the application of strong external electric field or the increase in temperature. Therefore, the electrical conduction is not possible as the free electrons are almost nil and hence these materials are called insulators. Its resistivity is in the range of 10¹¹ – 10¹⁹ Ωm.

Metals:
In metals, the valence band and conduction band overlap. Hence, electrons can move freely into the conduction band which results in a large number of free electrons in the conduction band. Therefore, conduction becomes possible even at low temperatures. The application of electric field provides sufficient energy to the electrons to drift in a particular direction to constitute a current. For metals, the resistivity value lies between 10^-2 and 10^-8 Ωm.

Semiconductors:
In semiconductors, there exists a narrow forbidden energy gap (E_g < 3 eV ) between the valence band and the conduction band. At a finite temperature, thermal agitations in the solid can break the covalent bond between the atoms (covalent bond is formed due to the sharing of electrons to attain stable electronic configuration). This releases some electrons from valence band to conduction band. Since free electrons are small in number, the conductivity of the semiconductors is not as high as that of the conductors. The resistivity value of semiconductors is from 10^-5 to 10⁶ Ωm.

Question 2.
Explain zener diode as a voltage regulator.
Answer:
Zener diode as a voltage regulator:
A Zener diode working in the breakdown region can serve as a voltage regulator. It maintains a constant output voltage even when input voltage V_i or load current I_L varies. Here, in this circuit the input voltage V_i is regulated at a constant voltage, V_z (Zener voltage) at the output represented as V₀ using a Zener diode. The output voltage is maintained constant as long as the input voltage does not fall belowV_z.

When the potential developed across the diode is greater than V_z ,the diode moves into the Zener breakdown region. It conducts and draws relatively large current through the series resistance R_i. The total current I passing through R_i equals the sum of diode current I_z and load current I_L (I = I_z + I_L) It is to be noted that the total current is always less than the maximum Zener diode current.
Under all conditions V₀ = V_z Thus, output voltage is regulated.

Question 3.
Write down the concept in details of Integrated Chips (IC’s) Integrated Chips
Answer:
An integrated circuit is also referred as an IC or a chip or a microchip. It consists of thousands to millions of transistors, resistors, capacitors, etc. integrated on a small flat piece of semiconductor material that is normally Silicon. Integrated circuits (ICs) are the keystone of modem electronics. With the advancement in technology and the emergence of Very Large Scale Integration (VLSI) era it is possible to fit more aind more transistors on chips of same piece.

ICs have two main advantages over ordinary circuits: cost and performance. The size, speed, and capacity of chips have progressed enormously with the advancement in technology. Computers, mobile phones, and other digital home appliances are now made possible by the small size and low cost of ICs. ICs can function as an amplifier, oscillator, timer, microprocessor and computer memory.

These extremely small ICs can perform calculations and store data using either digital or analog technology. Digital ICs use logic gates, which work only with values of ones and zeros. A low signal sent to a component on a digital IC will result in a value of 0, while a high signal creates a value of 1.

Samacheer Kalvi 12th Physics Semiconductor Electronics Numerical Problems

Question 1.
If the energy of a photon of sodium light (λ = 589 nm) equals the band gap of a semiconductor, calculate the minimum energy required to create hole-electron pair.
Solution:

Question 2.
In PNP transistor circuit, the collector current is 10 mA. If 90% of the holes reach the collector, find emitter and base currents.
Solution:
Here, I_E = 10 mA
As 90% of the holes reach the collector, so the collector current.
I_C = 90% of I_E
I_C = \(\frac { 90 }{ 100 }\) I_E
I_E = \(\frac { 100 }{ 90 }\) I_C = \(\frac { 100 }{ 90 }\) x 10
I_E ≃ 11mA
Base current, I_B = I_E – I_C = 11 – 10
I_B = 1 mA.

Question 3.
In the circuit, the value of β is 100. Find I_B, V_CE, V_BE and V_BC, when I_C = 1.5 mA. The transistor is in active, cut off or saturation state?
Solution:
β = 100; I_C = 1.5 mA= 1.5 x 10^-3 A, V_CC = 24 V
β = \(\frac {{ I }_{ C }}{{ I }_{ B }}\)
I_B = \(\frac {{ I }_{ C }}{β}\) = \(\frac { 1.5\times { 10 }^{ -3 } }{ 100 } \) = 15 μA
To calculate V_CE, We apply Kirchhoff’s rule to loop CEFDC, therefore
V_CC = I_C x 4.7 kΩ + V_CE
24 = 1.5 x 10^-3 x 4.7 10^-3 + V_CE
V_CE = 24 – 7.05 = 16.95 V

Again, applying Kirchhoff’s rule to loop ABEFDCA, We get,
V_CC = I_B x 220 kΩ + V_BE
V_CC = 15 x 10^-6 x 220 x 10^-3 + V_BE
V_BE  = 24 -3.3
V_BE = 20.7 V
Going along loop ABCA, we get
I_B x 220 kΩ + V_BC = I_c x 4.7 kΩ
15 x 10^-6 x 220 x 10³ + V_Bc = 1.5 x 10^-3 x 4.7 x 10³
V_BC = 7.05 -3.3 = 3.75 V
As V_CE < V_BE, both the junctions are forward biased. So, the transistor is in the saturation state.

Question 4.
A transistor has α = 0.95. If the emitter current is 10 mA, what is (a) the collector current, (b) the base current and (c) gain β?
Solution:
Here, α = 0.95, I_E = 10 mA
(a) α = \(\frac {{ I }_{ C }}{{ I }_{ E }}\) ⇒ I_C = αI_E = 0.95 x 10 = 9.5 mA
(b) I_B = I_E – I_C = 10 – 9.5 = 0.5 mA
(c) β = \(\frac { α }{ 1-α }\) = \(\frac { 0.95 }{ 0.05 }\) = 19.

Question 5.
For a BJT, the common-base current gain α = 0.98 and the collector base junction reverse bias saturation current I_C0= 0.6 μA. This BJT is connected in the common emitter mode and operated in the active region with a base drive current I_B = 20 μA. Find the collector current I_C for this mode of operation.
Solution:
α = 0.98 and I_C0= 0.6 μA
Collector current,
β = \(\frac { α }{ 1-α }\) = \(\frac { 0.98 }{ 1-0.98 }\) = 49
Thus,
I_C = (49 x 20) + (50 x 0.6) = 980 + 30 = 1010 μA
I_C = 1.01 μA.

Question 6.
An NPN BJT having reverse saturation current I_S = 10^-15 A is biased in the forward active region with V_BE = 700 mV and the current gain (β) may vary from 50 to 150 due to manufacturing variations. What is the maximum emitter current (in μA)
Solution:
I_S = 10^-15 A
V_BE = 700
V_T = 25 mV
β range from 50 to 150
I_C = I₀ e^(V_BE/V_T)
I_E = \(\frac { β+1 }{ β }\) I_C
I_E = \(\frac { β+1 }{ β }\) I_S e^V_BE/V_T
I_E will be maximum when β is 50
= 1.02 × 10^-15 × e^{700 × 10-3/25 × 10-3}
I_E = 1475 μA

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Tamilnadu Samacheer Kalvi 12th Commerce Solutions Chapter 26 Companies Act 2013

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Samacheer Kalvi 12th Commerce Companies Act 2013 Textbook Exercise Questions and Answers

I. Choose the correct answer

Question 1.
The Company will have to issue the notice of situation of Registered Office to the Registrar of Companies with in _____ days from the date of incorporation.
(a) 14 days
(b) 21 days
(c) 30 Days
(d) 60 Days
Answer:
(c) 30 Days

Question 2.
How does a person who envisages the idea to form a company called?
(a) Director
(b) Company Secretary
(c) Registrar
(d) Promoter
Answer:
(d) Promoter

Question 3.
For which type of capital a company pays the prescribed fees at the time of registration?
(a) Subscribed Capital
(b) Authorised Capital
(c) Paid-up Capital
(d) Issued Capital
Answer:
(b) Authorised Capital

Question 4.
Which of the following types of shares are issued by a company to raise capital from the existing shareholders?
(a) Equity Shares
(b) Right Shares
(c) Preference Shares
(d) Bonus Shares
Answer:
(b) Right Shares

Question 5.
Specify the type of resolution to be passed to choose the location of Registered Office of the company within the town or village or city.
(a) Ordinary
(b) Special
(c) Either Ordinary or Special
(d) Board
Answer:
(d) Board

Question 6.
Who can issue stock?
(a) Public
(b) Private
(c) One Person
(d) Small
Answer:
(a) Public

Question 7.
Specify the document which comes under the Negotiable Instrument Act.
(a) Share Certificate
(b) Share
(c) Share Warrant
(d) Stock
Answer:
(c) Share Warrant

Question 8.
The shares which are offered to the existing shareholder at free of cost is known as _____
(a) Bonus Share
(b) Equity Share
(c) Right Share
(d) Preference Share
Answer:
(a) Bonus Share

Question 9.
The shares which are offered first to the existing shareholder at reduced price is known as _____
(a) Bonus Share
(b) Equity Share
(c) Right Share
(d) Preference Share
Answer:
(c) Right Share

Question 10.
The Companies Act 2013 Prohibits the issue of shares at _____ to the public.
(a) Premium
(b) Par
(c) Discount
(d) Both at par and Premium
Answer:
(c) Discount

II. Very Short Answer Questions

Question 1.
Who is called as Promoters?
Answer:
Promotion stage begins when the idea to form a company comes in the mind of a person. The person who envisage the idea is called a ‘promoter’.

Question 2.
What is Share?
Answer:
The term Share is viewed by a layman as a fraction or portion of total capital of the company which have equal denomination.

Question 3.
What do you mean by Equity Share?
Answer:
The share of a company which do not have any preferential rights with regard to dividend and repayment of share capital at the time of liquidation of a company, is called as equity share or ordinary share.

Question 4.
What do you understand by Preference Share?
Answer:
The term ‘preference shares’ means that part of the share capital the holders of which have a preferential right over payment of dividend (fixed amount or rate) and repayment of share capital in the event of winding up of the company.

Question 5.
What is Sweat Equity Shares?
Answer:
Sweat Equity Shares means issue of shares to employees or directors at a lower price for cash or other than Cash.

Question 6.
What is Bonus Shares?
Answer:
Bonus share means to utilize the company’s reserves and surpluses. Issue of shares to existing shareholders without taking any consideration is known as Bonus Shares.

Question 7.
What is Right Shares?
Answer:
The right shares are primarily issued to the existing equity shareholders through a letter of an issue, on pro rata basis.

Question 8.
What is Private placement?
Answer:
Private placement means offer of securities or invitation to subscribe to securities to a select group of persons through private placement offer letter.

Question 9.
Define Share Warrant.
Answer:
A share warrant is a negotiable instrument, issued by the public limited company only against fully paid up shares. It is also termed as a document of title because the holder of the share warrant is entitled to the number of shares mentioned in it.

Question 10.
What is Debentures?
Answer:
When a company needs funds for extension and development purpose without increasing its share capital, it can borrow from the general public by issuing certificates for a fixed period of time and at a fixed rate of interest. Such a loan certificate is called a debenture.

III. Short Answer Questions

Question 1.
Distinguish between shares and stocks.
Answer:

Basis for Difference	Shares	Stocks
1. Meaning	The term ‘share’ means a fraction or unit of the total capital of the company which have equal denomination.	Stock is created from fully paid shares by passing resolution in the general meeting. The Articles of Association of the company must permit this conversion.
2. Denomination	All the shares are of equal denomination.	The denomination of stocks may. differ.
3. Paid up value	Shares can be partly or fully paid up.	Stock can only be fully paid up.

Question 2.
What do you understand by Issue of Securities at Premium?
Answer:
When shares are issued at a price above the face or nominal value, they are said to be issued at a premium. For example, a share having the face value of Rs. 10 is issued at Rs. 12. Here, Rs.2 is the premium. The amount of share premium has to be transferred to an account called the ‘ Securities Premium Account’

Question 3.
What is issue of shares at discount? What conditions should be fulfilled?
Answer:
When the shares are issued at a price below the face value they are said to be issued at a discount. For example, a share having the face value of Rs 10 is issued at Rs 8. The companies act 2013, prohibits the issue of shares at discount (Section 53), except sweat Equity share.

Question 4.
State condition stipulated for capital subscription at the time of promotion.
Answer:
For capital subscription, steps to be taken are listed below:

1. The fulfilling formalities to raise necessary capital.
2. Adhering to SEBI guidelines in this regard.
3. Observing guidelines for Disclosure and investor protection issued by SEBI.
4. Issuing prospectus.
5. Appointing official banker of the company for receiving application from the investors.

Question 5.
Explain different kinds of preference shares.
Answer:
There are eight types of preference shares:

1. Cumulative Preference shares: As the word indicates, all dividends are carried forward until specified.
2. Non-cumulative Preference shares: These are opposite of cumulative.
3. Redeemable Preference shares: Such preference shares can be claimed after a fixed period or after giving due notice. ,
4. Non-Redeemable Preference shares: Such shares cannot be redeemed during the lifetime of the company.
5. Convertible Preference shares: The shares can be converted into equity shares after a time period. .
6. Non-convertible Preference shares: Non-convertible preference shares cannot be, at any time, converted into equity shares.
7. Participating Preference shares.
8. Non-Participating Preference shares.

IV. Long Answer Questions

Question 1.
Write the difference between Debentures and Shares.
Answer:
Debentures:

1. Debentures mean a loan.
2. Debenture holder gets fixed rate of Interest.
3. Debentures generally have a charge on the assets of the company.
4. Debentures can be issued at a discount.
5. Debenture holders do not have any voting right.
6. Interest on debentures is payable even if there are no profits.
7. Interest paid on debenture is a business expense.

Shares:

1. Shares are part of the capital of a company.
2. Shareholders gets dividends with a varying rate.
3. Shares do not carry any such charge.
4. Shares cannot be issued at a discount.
5. Shareholders enjoy voting right.
6. Dividend is payable only if there is profit.
7. Dividend is not a business expense.

Question 2.
Brief different stages in Formation of a Company.
Answer:
Section 3 (1) of the Act states that a company may be formed for any lawful purpose by-
(a) seven or more persons, where the company to be formed is to be a public company;
(b) two or more persons, where the company to be formed is to be a private company;
(c) one person, where the company to be formed is to be One Person Company.
The process of formation of company consists of different stages:
1. Promotion: Promotion stage begins when the idea to form a company comes in the mind of a person.

2. Registration: The second stage in the formation of the company is incorporation or – registration. In this stage, the promoter has to fix name of the company, prepare the necessary documents (Memorandum and Articles of Association), fix the registered office, and name of the directors. After this, certificate of incorporation is issued.

3. Capital Subscription: A public limited company having its share capital has to pass through two stages. One of them is capital subscription. The steps for this is:

1. Formalities for raising capital
2. Issuing prospectus
3. Appointing official banker
4. Pass resolution to make allotment

4. Commencement of Business: As per section 11 of the Act, a company having share capital should file with the Registrar, declaration stating that

1. Every subscriber has paid the value of shares.
2. Paid up capital is not less than Rs.5 lakhs for a public limited company and Rs.1 lakh in case of a private limited company.
3. It has filed the Registrar, regarding the verification of registered office. After fulfilling these details, the Registrar will issue certificate of commencement of business.

Question 3.
What are the various kinds of Debentures?
Answer:
Debenture is a document issued by the company for acknowledging the loan from the public. Debentures are classified into different categories on the basis of:

1. Convertibility of the Instrument
2. Security of the Instrument
3. Redemption ability; and
4. Registration of Instrument.

1. On the basis of convertibility:
(a) Non-Convertible Debentures: These instruments cannot be converted into equity shares.
(b) Partly Convertible Debentures: Apart of these instruments are converted into equity shares.
(c) Fully Convertible Debentures: These are fully convertible into equity shares.
(d) Optionally Convertible Debentures: The investor can have the option to either convert the debentures at a price decided by the issuer or agreed upon at the time of issue.

2. On the basis of Security:
(a) Secured Debentures: These instruments are secured by a charge on the fixed assets of the issuer company.
(b) Unsecured Debentures: These instruments are unsecured against the assets.

3. On the basis of Redeemability:
(a) Redeemable Debentures: It refers to the debentures which will be redeemed in future.
(b) Irredeemable Debentures: It is a debenture, in which no specific time is specified by the companies to pay back the money.

4. On the basis of Registration:
(a) Registered Debentures: These are issued in the name of a particular person, who is registered by the company.
(b) Bearer Debentures: These are issued to the bearer and are negotiable instruments, and are transferred by mere delivery.

Question 4.
What formalities need to be fulfilled for companies having share capital to commence business?
Answer:
A public limited company having its share capital has to pass through two more stages. One of them is capital subscription, steps to be taken at this stage are listed below:

1. The fulfilling formalities to raise necessary capital.
2. Following the SEBI guidelines in this regard.
3. Issuing prospectus.
4. Appointing official banker of the company for receiving application from the investors.
5. Passing resolution for making allotment by director.
6. Despatch allotment letters to allottees.
7. Filing allotment return with the Registrar.
8. Issuing share certificates in exchange for their allotment letter.
9. Ensuring collection of minimum subscription.

Question 5.
Write the difference between Share Certificate and Share Warrant.
Answer:
Share Certificate:

1. A share certificate is an instrument in writing for the legal proof of the ownership.
2. Every company must issue share certificate to its shareholders.
3. Normally, the holder of the share certificate is to be the member of the company.
4. The share certificate is issued by the company within three months of the allotment of shares.
5. No need to authorized in the Articles of Association to issue share certificate.

Share Warrant:

1. A share warrant is a negotiable instrument, issued against fully paid up shares.
2. There is no compulsion of the issue of share warrants by the company.
3. Generally, the holder of the share warrant is not the member of the company.
4. Shares warrant can be issued only when the shares are fully paid up.
5. The issue of a share warrant must be authorized in the Articles of Association of the company.

Samacheer Kalvi 12th Commerce Companies Act 2013 Additional Questions and Answers

I. Choose the Correct Answer
Question 1.
Match List I with List II and select the correct answer using the codes given below:

Codes:

Answer:
(c) 3,1,4,2

Question 2.
The first two stages of formation of a company are
(i) Issue of prospectus
(ii) Promotion
(iii) Issue of share certificate
(iv) Registration
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (ii) and (iii)
(d) (i) and (iii)
Answer:
(b) (ii) and (iv)

We as a team believe the information prevailing regarding the Tamilnadu State Board Solutions for 26th Commerce Chapter 26 Companies Act 2013 Questions and Answers has been helpful in clearing your doubts to the fullest. For any other help do leave us your suggestions and we will look into them. Stay in touch to get the latest updates on Tamilnadu State Board Solutions for different subjects in the blink of an eye.

Enhance your subject knowledge with Tamilnadu State Board Solutions for 24th Commerce Chapter 24 Types of Entrepreneurs Questions and Answers and learn all the underlying concepts easily. Make sure to learn the subject from Tamilnadu State Board Solutions Chapter 24 Types of Entrepreneurs Questions and Answers PDF on a day to day basis and score well in your exams. You can Download Samacheer Kalvi 24th Commerce Book Solutions Questions and Answers are given after enormous research by people having high subject knowledge and for better scoring grade. You can rely on them and prepare any topic of Commerce as per your convenience easily.

Tamilnadu Samacheer Kalvi 12th Commerce Solutions Chapter 24 Types of Entrepreneurs

Students those who are looking for Tamilnadu State Board Solutions Chapter 24 Types of Entrepreneurs Questions and Answers Concepts can find them all in one place from our site Tamilnadu State Board Solutions. Simply click on the links available to prepare the corresponding topics of Samacheer Kalvi 24th Commerce Book Solutions Questions and Answers easily. Clarify all your queries from chapter wise different questions to be familiar with the kind of questions appearing in the exam. Thus, you can increase your score and get higher grade in the final exam.

Samacheer Kalvi 12th Commerce Types of Entrepreneurs Textbook Exercise Questions and Answers

I. Choose the Correct Answer

Question 1.
Choose the type of entrepreneur that isn’t based on function:
(a) Innovative
(b) Classical
(c) Fabian
(d) Drone
Answer:
(c) Fabian

Question 2.
Choose the type of Entrepreneur that is not based on Motivation:
(a) Pure
(b) Corporate
(c) Spontaneous
(d) Induced
Answer:
(c) Spontaneous

Question 3.
Which of the following is the Activity of a Business Entrepreneur?
(a) Production
(b) Marketing
(c) Operation
(d) All of the above
Answer:
(d) All of the above

Question 4.
Find the odd one out in context of Trading Entrepreneur.
(a) Selling
(b) Commission
(c) Buying
(d) Manufacturing
Answer:
(d) Manufacturing

Question 5.
Corporate Entrepreneur is also called as  _________
(a) Intrapreneur
(b) Promoter
(c) Manager
(d) Shareholder
Answer:
(b) Promoter

Question 6.
Poultry, Flowers, Fruits, etc., are called allied products of _________ entrepreneur.
(a) Corporate
(b) Retail
(c) Trading
(d) Agricultural
Answer:
(d) Agricultural

Question 7.
_________ Entrepreneur Supply Services Unlike.
(a) Hoteliers
(b) Banking
(c) Airlines
(d) Livestock
Answer:
(d) Livestock

Question 8.
Motive of a Pure Entrepreneur is _________
(a) Rendering service
(b) Earning profit
(c) Attaining status
(d) Both b and c
Answer:
(d) Both b and c

Question 9.
Which of these is based on Technology?
(a) Modem
(b) Professional
(c) Corporate
(d) Industrial
Answer:
(c) Corporate

Question 10.
Which of the below is not a characteristic of a Fabian Entrepreneur?
(a) Conservative
(b) Risk averse
(c) Sceptical
(d) Adaptive
Answer:
(d) Adaptive

II. Very Short Answer Questions

Question 1.
What is the other name of business entrepreneur?
Answer:
The term entrepreneur means the. person who takes steps for commencing the business. So he is otherwise called as organiser or proprietor.

Question 2.
Mention the other name for corporate entrepreneur.
Answer:
Corporate entrepreneur is called promoter. He/she takes initiative necessary to start an entity under corporate format.

Question 3.
Who are agricultural entrepreneur?
Answer:
Agricultural entrepreneurs are those entrepreneurs who raise farm products and market them.

Question 4.
State the name of the.following ventures:
a. Started by individuals for profit motive
b. Started by Government
c. Started by individuals and Government together
d. Started as a family business
Answer:
a. Private entrepreneur
b. State entrepreneurship
c. Induced entrepreneur
d. Classical entrepreneur

Question 5.
Give some examples of pure entrepreneurs.
Answer:
Dhirubai Ambani, Jamshedji Tata, T.V. Sundaram Iyengar, Seshadriji, Birla, Narayanamurthi, and Azim Premji are few examples of pure entrepreneurship.

III. Short Answer Questions

Question 1.
Who is a private entrepreneur?
Answer:
Ventures started by individual either singly or collectively at their own risk after mobilising – various, resources in order to earn profit are called private entrepreneurship.

Question 2.
What is political environment?
Answer:
To commence business, various factors are needed. Apart from all other factors, political environment is also essential. It means that the concessions, incentives provided by the government drive them to enter into venture. The government also provides support in the form of loans, subsidies and other taxes.

Question 3.
List down few examples of pure entrepreneurship.
Answer:
Pure entrepreneurs are individuals who are propelled to enter into venture by psychological and economic motives. They nurture desire of starting a particular venture and earning high profit there from and thus attaining a social status. They apply their knowledge, skill and insight in making the venture a great’ success in order to earn maximum profit out of the venture. Dhirubai Ambani, Jamshedji Tata, T.V. Sundaram Iyengar, Seshadriji, Birla, Narayanamurthi, and Azim Premji are few examples of pure entrepreneurship.

Question 4.
How does a professional entrepreneur operate?
Answer:
Professional entrepreneur is one who is having a rich expertise in starting a venture but lack interest in continuing the venture as a manager or as a owner. He/she simply sells out the venture started by him to someone else after its successful take-off.

Question 5.
Explain, about the agricultural entrepreneur.
Answer:
Agricultural entrepreneurs are those entrepreneurs who raise farm products and market them. They use the various inputs like labour, fertilizer, insecticide, water technology, etc., to raise the products and market their products either directly or through co-operative entities or through brokers or through tie up with large retailers.

IV. Long Answer Questions

Question 1.
Explain in detail on classification according to the type of business.
Answer:
Classification of Entrepreneur according to the type of business:

(i) Business Entrepreneur: He is called solo entrepreneur. He is the one who finds out an idea for a new product or service and establish a business enterprise.

(ii) Trading Entrepreneur: Trading entrepreneurs are those who restrict themselves to buying and selling finished goods.

(iii) Industrial Entrepreneur: These are entrepreneurs who manufacture products to cater to

(iv) Corporate Entrepreneur: He is called as promoter. He takes initiative necessary to start an entity under corporate format.

(v) Agricultural Entrepreneur: These entrepreneurs are those who raise farm products and market them.

Question 2.
Discuss the nature of functional entrepreneurs.
Answer:
Nature of functional entrepreneurs:

(i) Innovative Entrepreneur: He is a person who introduces new project. They observe the environment regarding information to the new venture.

(ii) Imitative Entrepreneur: He refers to the person who simply imitates existing knowledge or technology already in advance countries. Redesigning of products suited to the local conditions.

(iii) Fabian Entrepreneur: These are said to be conservatives and sceptical about any changes in their organisation. They are of risk-averse.

(iv) Drone Entrepreneur: Drone entrepreneurs are those who are totally opposed to changes in the environment. They used to operate in the-niche market.

Question 3.
Distinguish between the rural and urban entrepreneur.
Answer:

S. No.	Rural Entrepreneur	Urban Entrepreneur
1.	It refers to the person who starts business in rural areas.	It refers to the person who commences business in urban areas.
2.	These entrepreneurs start doing business in the villages and small towns.	They will do their business in state capital, towns, district headquarters, municipalities, etc.
3.	They may be agricultural and trading entrepreneurs.	They may be industrial or corporate entrepreneur.
4.	The availability of material and labour is easy. So the cost of operation tends to be low.	The availability of material and labour may be difficult. So the cost of operation may be high.

Samacheer Kalvi 12th Commerce Types of Entrepreneurs Additional Questions and Answers

I. A. Choose the Correct Answer

Question 1.
The entrepreneurs classified on the basis of type of business are __________
(i) Industrial entrepreneur
(ii) Technical entrepreneur
(iii) Professional entrepreneur
(iv) Business entrepreneur
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
Answer:
(b) (i) and (iv)

B. Fill in the blanks

Question 1.
Entrepreneur who commences his entrepreneurial activity in urban areas is called as __________
Answer:
urban entrepreneur

II. Very Short Answer Questions

Question 1.
Who is a service entrepreneur?
Answer:
The entrepreneurs enter into the business of giving service products to end consumers. Example: Banking, Insurance and Transport services.

Question 2.
Write a short note on retail entrepreneurs.
Answer
Retail entrepreneurs are those who enter into venture of distributing the end product to final consumer. They used to buy the goods from numerous wholesalers.

III. Short Answer Questions

Question 1.
Who are industrial entrepreneurs?
Answer:
Industrial entrepreneurs are those persons who manufacture products to cater the needs of the consumers. They may be small, medium and large entrepreneurs. Industrial entrepreneurs mobilise the resources of various types’.

Question 2.
Who are technical entrepreneurs?
Answer:
Technical entrepreneurs are those craftsmen like welder, fitter, turner, carpenter and goldsmith, photographer, weaver who start small business. They manufacture products/service of high quality. They simply focus on production rather than on marketing.

We as a team believe the information prevailing regarding the Tamilnadu State Board Solutions for 24th Commerce Chapter 24 Types of Entrepreneurs Questions and Answers has been helpful in clearing your doubts to the fullest. For any other help do leave us your suggestions and we will look into them. Stay in touch to get the latest updates on Tamilnadu State Board Solutions for different subjects in the blink of an eye.

Enhance your subject knowledge with Tamilnadu State Board Solutions for 23th Commerce Chapter 23 Elements of Entrepreneurship Questions and Answers and learn all the underlying concepts easily. Make sure to learn the subject from Tamilnadu State Board Solutions Chapter 23 Elements of Entrepreneurship Questions and Answers PDF on a day to day basis and score well in your exams. You can Download Samacheer Kalvi 23th Commerce Book Solutions Questions and Answers are given after enormous research by people having high subject knowledge and for better scoring grade. You can rely on them and prepare any topic of Commerce as per your convenience easily.

Tamilnadu Samacheer Kalvi 12th Commerce Solutions Chapter 23 Elements of Entrepreneurship

Students those who are looking for Tamilnadu State Board Solutions Chapter 23 Elements of Entrepreneurship Questions and Answers Concepts can find them all in one place from our site Tamilnadu State Board Solutions. Simply click on the links available to prepare the corresponding topics of Samacheer Kalvi 23th Commerce Book Solutions Questions and Answers easily. Clarify all your queries from chapter wise different questions to be familiar with the kind of questions appearing in the exam. Thus, you can increase your score and get higher grade in the final exam.

Samacheer Kalvi 12th Commerce Elements of Entrepreneurship Textbook Exercise Questions and Answers

I. Choose the Correct Answer

Question 1.
Which of the below is a factor of production?
(a) Land
(b) Labour
(c) Entrepreneurship
(d) All of the above
Answer:
(d) All of the above

Question 2.
Entrepreneur is not classified as ________
(a) Risk Bearer
(b) Innovator
(c) Employee
(d) Organizer
Answer:
(b) Innovator

Question 3.
What are the characteristics of an entrepreneur?
(a) Spirit of enterprise
(b) Flexibility
(c) Self Confidence
(d) All of the above
Answer:
(d) All of the above

Question 4.
Which of the below is not classified into managerial functions?
(a) Planning
(b) Marketing
(c) Organizing
(d) Controlling
Answer:
(c) Organizing

Question 5.
Which of the below is a commercial function?
(a) Accounting
(b) Coordination
(c) Discovery of idea
(d) Planning
Answer:
(a) Accounting

II. Very Short Answer Questions

Question 1.
Mention any two features of entrepreneurs.
Answer:
Features of Entrepreneurs:

1. Spirit of Enterprise: Entrepreneur should be bold enough to encounter risk arising from the venture undertaken.
2. Self Confidence: Entrepreneur should have a self confidence in order to achieve high goals in the business.

Question 2.
List down the managerial functions of entrepreneurs.
Answer:

1. Planning
2. Organising
3. Directing
4. Controlling
5. Coordination

Question 3.
List down the promotional functions of entrepreneurs.
Answer:

1. Discovery of Idea
2. Determining the business objectives
3. Detailed Investigation
4. Choice of form of enterprise
5. Fullfillment of the formalities
6. Preparation of Business Plan
7. Mobilisation of funds
8. Procurement of Machines and Materials

Question 4.
Define Intrapreneur.
Answer:
Intrapreneur is one who thinks and acts like an entrepreneur for the firm’s development during the course of employment in an organisation.

Question 5.
List the problems faced by the women entrepreneurs.
Answer:
There is a tremendous growth in the women entrepreneurship in India. But there are certain problems met by women entrepreneurs. They are as follows:-

1. Problem of Finance: The external sources of funds for the women is limited because they do not generally own properties in their own name. They are depending on their own savings and small loans from friends and relatives.
2. Lack of Education: Illiterate and semi-literate women entrepreneurs face difficulties in respect of accounts, money matters, marketing and day-to-day operations.
3. Lack of Network Support: The success of business depends on the support of family members, friends and relatives. But it is reported that the women entrepreneurs get very limited support in times of crisis.
4. Stiff Competition: They have to face acute competition for their goods from organised sector and from their male counterparts.
5. Lack of Information: The lack of knowledge or limited knowledge about subsidies, concessions and incentives given by Government will affect the business.

III. Short Answer Questions

Question 1.
Define Entrepreneur.
Answer:
The person who establishes business is termed as entrepreneur. The output of an entrepreneurial process ends up in establishing an enterprise.

Question 2.
Distinguish between Entrepreneur and Manager.
Answer:

Basis of difference	Entrepreneur	Manager
Motive	The very motive of an entrepreneur is to start a venture by setting of an entity.	The very motive of manager is to render service in an entity setup for execution of venture.
Status	Entrepreneur is owner of the entity.	Manager is a salaried employee in the entity set up for carrying on the venture.
Risk Bearing	Entrepreneur bears the eventual risk and uncertainty in operating the enterprise.	Manager doesn’t bear any risk in the venture, where the venture is unsuccessful he/she simply quits the enterprise.

Question 3.
List down the commercial functions of Entrepreneur and explain them shortly.
Answer:
Commercial Functions of Entrepreneur:

(i) Production or Manufacturing: Under production function, entrepreneur has to take decision relating to selection of factory site, design and layout, type of products to be manufactured, research and development, product design, etc.

(ii) Marketing: Entrepreneur has to carry out following functions pertaining to marketing aspect namely consumer research, product planning and development, standardisation, packaging, pricing, warehousing, distribution, promotion etc.

(iii) Accounting: Entrepreneur has to arrange to prepare trading and profit and loss account in order to know the profit or loss incurred out of operation of the business and prepare balance sheet to know the financial status of business at a particular day.

(iv) Finance: In the sphere of financial function, an entrepreneur has to take decisions like choosing the right type of financing, framing the best dividend policy, acquiring of funds, efficiently managing fixed and current assets, maximising shareholders wealth and investing of funds efficiently and effectively.

(v) Human Resource Management: Entrepreneur has to estimate the manpower needs of the enterprise and accordingly decide the size of manpower required for various slots of organisational structure.

Question 4.
Explain the promotional functions of entrepreneur.
Promotional Functions of Entrepreneur
Answer:
(i) Discovery of Idea: The first and foremost function of entrepreneur is idea generation. A person may conceive his own ideas or develop the ideas contributed by others. Ideas can be generated through several ways like own experience and exposure of entrepreneur, keen observation of environment, education, training, market survey, environmental scanning and so on.

(ii) Determining the business objectives: Entrepreneur has to develop business objectives in the backdrop of nature of business and type of business activity i.e. nature of business, manufacturing or trading, type of business organisation chosen so that he/she can organise the venture in accordance with the objectives determined by him/her.

(iii) Detailed Investigation: Entrepreneur should investigate commercial feasibility of the product proposed to be produced and conduct market study to ascertain the potential demand for the product.

(iv) Choice of form of enterprise: Entrepreneur has to choose the appropriate form of organisation suited to implement the venture. There are various forms of organisation namely sole proprietor, partnership, company and co-operatives etc. which are in existence.

(v) Fulfilment of the formalities: Having chosen the appropriate type of organisation, entrepreneur has to take necessary steps to establish the form of organisation chosen. As regards sole trader, the formalities are barest minimum. In the case of partnership firm, entrepreneur has to arrange for partnership deed and he has to get the deed registered.

(vi) Preparation of Business Plan: Entrepreneur has to prepare a business plan or project report of the venture that he is proposing to take up.

(vii) Mobilisation of funds: Entrepreneur has to take steps to mobilise capital needed to implement the venture. Entrepreneur has to estimate the fixed capital and working capital required for running the project.

(viii) Procurement of Machines and Materials: Entrepreneur has to locate the various sources of supply of machineries, equipments and materials.

Question 5.
Explain the commercial functions of entrepreneur.
Answer:
(i) Production or Manufacturing: Under production function, entrepreneur has to take decision relating to selection of factory site, design and layout, type of products to be manufactured, research and development, product design, etc. The efficient and effective performance of production function depends on the proper production planning and control to a major extent.

(ii) Marketing: Entrepreneur has to carry out following functions pertaining to marketing aspect namely consumer research, product planning and development, standardisation, packaging, pricing, warehousing, distribution, promotion etc. The term marketing mix denotes the combination of four components namely product, price, promotion and physical distribution in the case of physical products and three more components are included in the case of service products namely people, process and physical evidence.

(iii) Accounting: Entrepreneur has to arrange to prepare trading and profit and loss account in order to know the profit or loss incurred out of operation of the business and prepare balance sheet to know the financial status of business at a particular day. Besides, cash flow and fund flow statements are prepared to ensure the adequacy of funds and cash for meeting various working capital needs of the business.

(iv) Finance: In the sphere of financial function, an entrepreneur has to take decisions like choosing the right type of financing, framing the best dividend policy, acquiring of funds, efficiently managing fixed and current assets, maximising shareholders wealth and investing of funds efficiently and effectively.

(v) Human Resource Management: Entrepreneur has to estimate the manpower needs of the enterprise and accordingly decide the size of manpower required for various slots of organisational structure. After determining the required manpower, the entrepreneur has to organise for recruitment procedure

selecting manpower, induction and training, determining compensation structure and incentives, designing motivation programmes, structuring wellbeing measures for employees, putting in place safety mechanism at workplace, performance evaluation and career advancement and structuring social security programmes.

IV. Long Answer Questions

Question 1.
How do you classify entrepreneurs?
Answer:
Entrepreneurs are now broadly classified into three groups namely risk bearer, organiser and
innovator.

1. Entrepreneur as a risk bearer : Entrepreneurs acts as an agent combining all factors of production to produce a product or service in order to sell at uncertain price in future.

2. Entrepreneur as an organiser : Entrepreneur is one who brings together various factors of production and creates an entity to produce product or service and supervise and coordinates several functions in the process.

3. Entrepreneur as an innovator : According to Joseph A. Schumpeter in the year 1934 used innovation as a criterion to define an individual as entrepreneur. According to him, entrepreneur is one who

• • Introduces a brand new product in the market.
  • Institutes new technology to produce a new product.
  • Discovers new course of supply of raw materials.

Question 2.
What are the characteristics of an entrepreneur?
Answer:
Characteristics of an Entrepreneur:

1. Spirit of Enterprise: Entrepreneur should be bold enough to encounter risk arising from Elements of Entrepreneurship 145 the venture undertaken.

2. Self-confidence: Entrepreneur should have self-confidence in order to achieve high goals in the business.

3. Flexibility: Entrepreneur should not doggedly stick to decisions in a rigid fashion.

4. Innovation: Entrepreneur should contribute something new or something unique to meet the changing requirements of customers namely new product, new method of production or distribution, adding new features to the existing product, uncovering a new territory for business, innovating new raw material, etc.

5. Resource Mobilisation: Entrepreneur should have the capability to mobilise both tangible inputs like manpower, money materials, technology, market, method etc., which are scattered over a wide area and certain intangible inputs like motivation, morale and innovativeness.

Question 3.
Distinguish between an Entrepreneur and an Intrapreneur.
Answer:

Question 4.
Discuss the problems faced by Women Entrepreneurs.
Answer:
There is a tremendous growth in the women entrepreneurship in India. But there are certain problems met by women entrepreneurs.
They are as follows:-

1. Problem of Finance: The external sources of funds for the women is limited because they do not generally own properties in their own name. They are depending on their own savings and loan from friends and relatives.
2. Lack of Education: Illiterate and semi-literate women entrepreneurs face difficulties in respect of accounts, money matters, marketing and day-to-day operations.
3. Lack of Network Support: The success of business depends on the support of family members, friends and relatives. But it is reported that the women entrepreneurs get very limited support in times of crisis.
4. Stiff Competition: They have to face acute competition for their goods from organised sector and from their male counterparts.
5. Lack of Information: The lack of knowledge or limited knowledge about subsidies, concessions and incentives given by Government will affect the business.

Question 5.
Explain in detail the various functions of an entrepreneur.
Answer:
The functions of an entrepreneur is divided into
(a) Promotional functions,
(b) Managerial functions
(c) Commercial functions.

(a) Promotional functions:
(i) Discovery of Idea: The first and foremost function of entrepreneur is idea generation. A person may conceive his own ideas or develop the ideas contributed by others. Ideas can be generated through several ways like own experience and exposure of entrepreneur, keen observation of environment, education, training, market survey, environmental scanning and so on.

(ii) Detailed Investigation: Entrepreneur should investigate commercial feasibility of the product proposed to be produced and conduct market study to ascertain the potential demand for the product.

(iii) Mobilisation of funds: Entrepreneur has to take steps to mobilise capital needed to implement the venture. Entrepreneur has to estimate the fixed capital and working capital required for running the project.

(b) Managerial functions:
(i) Planning: In this function, the entrepreneur has to lay down the objectives, goals, vision, mission, policies, procedures, programmes, budget, schedules etc., for enabling the venture to proceed towards established destinations.

(ii) Directing: In this function, the entrepreneur has to motivate, lead, guide and communicate with subordinates on an ongoing basis in order to accomplish pre-set goals.

(c) Commercial functions:
(i) Production or Manufacturing: Under production function, entrepreneur has to take decision relating to selection of factory site, design and layout, type of products to be manufactured, research and development.

(ii) Accounting: Entrepreneur has to arrange to prepare trading and profit and loss account in order to know the profit or loss incurred out of operation of the business and prepare balance sheet to know the financial status of business.

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Tamilnadu Samacheer Kalvi 12th Commerce Solutions Chapter 22 The Negotiable Instruments Act 1881

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Samacheer Kalvi 12th Commerce The Negotiable Instruments Act 1881 Textbook Exercise Questions and Answers

I. Choose the Correct Answer

Question 1.
Negotiable Instrument Act was passed in the year ________
(a) 1981
(b) 1881
(c) 1994
(d) 1818
Answer:
(b) 1881

Question 2.
Negotiable Instrument is freely transferable by delivery if it is a ________ instrument.
(a) Order
(b) Bearer
(c) Both a and b
(d) None of the above
Answer:
(b) Bearer

Question 3.
The transferee of a Negotiable Instrument is the one ________
(a) Who transfer the instrument
(b) On whose name it is transferred
(c) Who enchases it
(d) None of the above
Answer:
(b) On whose name it is transferred

Question 4.
Number of parties in a bill of exchange are ________
(a) 2
(b) 6
(c) 3
(d) 4
Answer:
(c) 3

Question 5.
Section 6 of Negotiable Instruments Act 1881 deals with ________
(a) Promissory Note
(b) Bills of exchange
(c) Cheque
(d) None of the above
Answer:
(c) Cheque

Question 6.
________ cannot be a bearer instrument.
(a) Cheque
(b) Promissory Note
(c) Bills of exchange
(d) None of the above
Answer:
(a) Cheque

Question 7.
When crossing restrict further negotiation ________
(a) Not negotiable crossing
(b) General Crossing
(c) A/c payee crossing
(d) Special crossing
Answer:
(a) Not negotiable crossing

Question 8.
Which endorsement relieves the endorser from incurring liability in the event of dishonour?
(a) Restrictive
(b) Facultative
(c) Sans recourse
(d) Conditional
Answer:
(b) Facultative

Question 9.
A cheque will become stale after ________ months of its date.
(a) 3
(b) 4
(c) 5
(d) 1
Answer:
(a) 3

Question 10.
Document of title to the goods exclude ________
(a) Lorry receipt
(b) Railway receipt
(c) Airway bill
(d) Invoice
Answer:
(d) Invoice

II. Very Short Answer Questions

Question 1.
What is meant by Negotiable Instrument?
Answer:
A negotiable instrument is a document which entitles a person to a certain sum of money and which is transferable from one person to another by mere delivery or by endorsement and delivery.

Question 2.
Define Bill of Exchange.
Answer:
According to section 5 of the Negotiable Instruments Act, “a bill of exchange is an instrument in writing containing an unconditional order, signed by the maker, directing a certain person to pay a certain sum of money only to, or to the order of a certain person or to the bearer of the – instrument”.

Question 3.
List three characteristics of a Promissory Note.
Answer:
Characteristics of a Promissory Note:

1. A promissory note must be in writing.
2. The promise to pay must be unconditional.
3. It must be signed by the maker.

Question 4.
What is meant by a cheque?
Answer:
According to section 6 of the Negotiable Instruments Act, 1881 defines a cheque as “a bill of exchange drawn on a specified banker and not expressed to be payable otherwise than on demand”.

Question 5.
Define Endorsement.
Answer:
“When the maker or holder of a negotiable instrument signs the name, otherwise that as such maker for the purpose of negotiation, on the back or face thereof, or on a slip of paper annexed thereto.”

III. Short Answer Questions

Question 1.
Explain the nature of a Negotiable Instrument.
Answer:
A negotiable instrument is transferable from one person to another without any formality, such as affixing stamp, registration, etc. When the instrument is held by holder in due course in the process of negotiation, it is cured of all defects in the instrument with respect to ownership. Though a bill, a promissory note or a cheque represents a debt, the transferee is entitled to sue on the instrument in his own name in case of dishonour, without giving notice to the debtor that he has become its holder.

Question 2.
Distinguish between Negotiability and Assignability.
Answer:

Question 3.
What are the characteristics of a bill of exchange?
Answer:
Characteristics of a Bill of Exchange:

1. A bill of exchange is a document in writing.
2. The document must contain an order to pay.
3. The order must be unconditional.
4. The instrument must be signed by the person who draws it.
5. The name of the person on whom the bill is drawn must .be specified in the bill itself.

Question 4.
Distinguish between Bill of Exchange and Promissory Note.
Answer:

IV. Long Answer Questions

Question 1.
Mention the presumptions of Negotiable Instruments.
Answer:
Presumptions of Negotiable Instrument:

1. Every negotiable instrument is presumed to have been drawn and accepted for consideration.
2. Every negotiable instrument bearing, a date is presumed to have been made or drawn on such a date.
3. It is presumed to have been accepted within a reasonable time after the date and before its maturity.
4. The transfer of a negotiable instrument is presumed to have been made before maturity.
5. When a negotiable instrument has been lost, it is presumed to have been duly stamped.
6. The holder of a negotiable instrument is presumed to be a holder in due course.

Question 2.
Distinguish a cheque and a bill of exchange.
Answer:

Question 3.
Discuss in detail the features of a cheque.
Answer:
A cheque is a negotiable instrument drawn on a particular banker.
Features:
(i) Instrument in Writings:
A cheque or a bill or a promissory note must be an instrument in writing. Though the law does not prohibit a cheque being written in pencil, bankers never accept it because of risks involved. Alternation is quite easy but detection is impossible in such cases.

(ii) Unconditional Orders:
The instrument must contain an order to pay money. It is not necessary that the word ‘order’ or its equivalent must be used to make the document a cheque. It does not cease to be a cheque just because the world ‘please’ is used before the word pay. Further the order must be unconditional.

(iii) Drawn on a Specified Banker Only:
The cheque is always drawn on a specified banker. A cheque vitally differs from a bill in this respect as latter can be drawn on any person including a banker. The customer of a banker can draw the cheque only on the particular branch of the bank where he has an account.

(v) A Certain Sum of Money Only:
The order must be for payment of only money. If the banker is asked to deliver securities, the document cannot be called a cheque. Further, the sum of money must be certain.

(v) Payee to be Certain:
The cheque must be made payable to a certain person or to the order of a certain person or to the bearer of the instrument. The word, person includes corporate bodies, local authorities, associations, holders of office of an institution etc.

(vi) Signed by the Drawer:
The cheque is to be signed by the drawer. Further, it should tally with specimen signature furnished to the bank at the time of opening the account.

Question 4.
What are the requisites for a valid endorsement?
Answer:
If an endorsement is to be valid, it must possess the following requisites:

1. Endorsement is to be made on the face of the instrument or on its back.
2. When there is no space for making further endorsements a piece of paper can be attached
3. Endorsement for only a part of the amount of the instrument is invalid.
4. Endorsement is complete only when delivery of the instrument is made.
5. Signing in block letters does not constitute regular endorsement.
6. If the payee is an illiterate person, he can endorse it by affixing his thumb impression on the instrument.

Question 5.
Explain the different kinds of endorsements. .
Answer:
When the person signs on the back of the instrument to transfer his interest, it is known as endorsement. The endorsement are of various types:
(i) Blank or general endorsement:
When the endorser puts his mere signature on the back of an instrument without mentioning the name of the person to whom the endorsement is made, it is called Blank Endorsement

(ii) Endorsement in full or special endorsement:
If the endorser, in addition to his signature, mentions the name of the person to whom it is endorsed, is known as endorsement in full or special endorsement.

(iii) Conditional endorsement:
When the endorser of a negotiable instrument makes his liability dependent upon the happening of an event which may or may not happen, it is called conditional endorsement,

(iv) Restrictive endorsement:
When an endorsement restricts or prohibits further negotiability of the instrument, it is called Restrictive Endorsement.

(v) Partial Endorsement:
Where the endorsement seeks to transfer only a part of the amount payable under the instrument, the endorsement is called Partial Endorsement.

Samacheer Kalvi 12th Commerce The Negotiable Instruments Act 1881 Additional Questions and Answers

I. Choose the Correct Answer

Question 1.
A bill of exchange drawn on a specified banker is
(a) promissory note
(b) cheque
(c) hundi
(d) share
Answer:
(b) cheque

Question 2.
Grace days allowed to a Bill of exchange for calculation of due date is
(a) 4
(b) 10
(c) 3
(d) 5
Answer:
(c) 3

We as a team believe the information prevailing regarding the Tamilnadu State Board Solutions for 22th Commerce Chapter 22 The Negotiable Instruments Act 1881 Questions and Answers has been helpful in clearing your doubts to the fullest. For any other help do leave us your suggestions and we will look into them. Stay in touch to get the latest updates on Tamilnadu State Board Solutions for different subjects in the blink of an eye.