Question 1.
The biggest source of energy on Earths surface is?
Year of Question :(2012)

• (a) Biomass
• (b) Solar radiations
• (c) Tides
• (d) Winds (2020)

Answer:

• (b) The biggest source of energy on Earths surface is solar radiations
• Answer question numbers 2-5 on the basis of your understanding of the following paragraph and the related studied concepts: The Tehri dam is the highest dam in India and one of the highest in the World. The Tehri dam withholds a reservoir of capacity 4.0 km³ and surface area 52 km². It is used for irrigation, municipal water supply and the generation of 1000 MW of hydro electricity
• The Tehri Dam has been the object of protests. Environment activist Shri Sunder Lai Bahuguna led the "Anti Tehri Dam Movement" from 1980s to 2014. The protest was against the displacement of town inhabitants and environmental consequences of the weak ecosystem. The relocation of more than 1,00,000 people from the area has led to protracted legal battles over resettlement rights and ultimately resulted in the delayed completion of the project. (2020)

Question 2.
How is hydropower harnessed?
Year of Question :(2017)

Answer: Potential energy of water stored in a dam is converted into kinetic energy of falling water and then, this kinetic energy is converted into electrical energy

Question 3.
Define 1 MW?
Year of Question :(2012)

Answer: 1 MW is the power consumed or dissipated by a device which consumes or dissipates 1 mega joule of energy per second

Question 4.
Mention two disadvantages of constructing Tehri Dam?
Year of Question :(2012)

Answer: For the construction of Tehri Dam, relocation of more than 100000 people was needed which led to widespread protests and legal battles. Also large ecosystems were destroyed when it submerged under the water in dams causing emission of large amounts of methane which is a green-house gas

Question 5.
What happens when water from great heights is made to fall on blades of turbine?
Year of Question :(2012)

Answer: When water from great heights is made to fall, the potential energy of these waters get converted into kinetic energy and when it falls on the blades of turbines, it rotates the turbine of a generator, thus producing electricity

Question 6.
Why is biogas considered an excellent fuel?
Year of Question :(2019)

Answer: Biogas is considered as excellent fuel because

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• it does not produce smoke
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• slurry left behind can be used as an excellent manure
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Question 7.
Name any two nutrients that the spent slurry has in the biogas plant?
Year of Question :(2019)

Answer: Nitrogen and phosphorus

Question 8.
Write the energy conversion that takes place in a hydropower plant?
Year of Question :(2012)

Answer: Hydropower plant converts the potential energy of stored yrater into electrical energy

Question 9.
Name any two fossils fuels?
Year of Question :(2017)

Answer: Coal and petroleum are two fossil fuels

Question 10.
Name any two conventional sources of energy.?
Year of Question :(2012)

Answer:

• (i) Fossil fuels
• (ii) Wind energy

Question 11.
What is meant by the term Biomass?
Year of Question :(2014)

Answer: Biomass : Cow-dung, various plant materials like the residue after harvesting the crops, vegetable wastes and sewage which can be decomposed in the absence of oxygen is called biomass

Question 12.
Write the characteristic features of the micro organisms which help in the production of biogas in a biogas plant?
Year of Question :(2014)

Answer: In a biogas plant, anaerobic micro-organisms are used. They do not require oxygen to decompose or break-down complex compounds of the cow- dung slurry

Question 13.
What are fossil fuels? "Burning fossil fuels may lead to intense global warming." Justify this statement?
Year of Question :(2014)

Answer: Fossil fuels : The combustible substances formed from the dead remains of the animals and plants which were buried deep under the surface of the earth for over millions of years are called fossil fuels. Burning of fossil fuels produces carbon dioxide and excess carbon dioxide in the atmosphere causes the greenhouse effect, leading to intense global warming

Question 14.
What is the main constituent of biogas? How is biogas obtained from biomass? Write any two advantages of using this gas?
Year of Question :(2011)

Answer: Tlie main constituent of biogas is methane (75%). Biogas is obtained by anaerobic decomposition of biomass in a biogas plant. The two advantages of using this gas are

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• It does not produce smoke
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• It has high calorific value
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Question 15.
Define?
Year of Question :(2011)

• (i) Biomass
• (ii) Anaerobic degradation (Foreign 2011)

Answer:

• (i) Anaerobic degradation : Breaking of large organic molecules into simple molecules in the absence of air is called anaerobic degradation

Question 16.
There are many limitations associated with the setting up of wind energy farms to harness energy. Raman wants to generate electricity by using wind mill in his parental village in Uttar Pradesh?
Year of Question :(2016)

• (i) Is it advisable to set up such wind energy farms in his village? Give reason for your answer
• (ii) Write any two limitations associated with the wind energy farms
• (iii) Write the energy transformations which take place when wind mill is used for generating electricity? (Board Term I, 2016)

Answer:

• (i) No, it is not advisable to set up such wind energy farms in his village because wind energy farms can be established only at those places where wind blows for the greater past of a year. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine
• (ii) Limitation of wind energy
• (a) Initial cost of establishment of the farm is quite high
• (b) The tower and blades need a high level of maintenance.

Question 17.
Explain with the help of labelled diagram the process of production of biogas in a biogas plant?
Year of Question :(2013)

Answer: Working of the biogas plant: Dung and domestic/agricultural wastes are mixed with water in the mixing tank. The slurry so obtained is fed into the digester through the inlet chamber. Gradually, the anaerobic fermentation sets in and biogas is produced. It takes about 6-8 weeks for a new biogas plant to start producing biogas at a reasonably fast rate. When the pressure of biogas inside the dome increases, it starts pushing the spent slurry into the outlet chamber, and finally into the overflow tank. The spent slurry being a rich source of plant nutrients is used as a manure in agricultural fields. Biogas can be taken out for supply by spinning the gas valve. To make the biogas plant run continuously, dung slurry is fed into the digester and the spent slurry is removed from it from time to time

Question 18.
List any four disadvantages of using fossil fuels for the production of energy?
Year of Question :(2011)

Answer: Disadvantages of using fossil fuels for the production of energy are

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• Fossil fuels are non-renewable source of energy
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• It causes air pollution to the environment
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• It takes millions of years for its formation
?It causes acid rain

Question 19.
Which one of the following statement is not true about nuclear energy generation in a nuclear reactor?
Year of Question :(2013)

• (a) Energy is obtained by a process called nuclear fission
• (b) The nucleus of Uranium is bombarded with high energy neutrons
• (c) A chain reaction is set in the process
• (d) In this process a tremendous amount of energy is released at a controlled rate. (2020)

Answer:

• (b) In a nuclear reactor, to produce nuclear energy, uranium is bombarded with low energy neutrons

Question 20.
Assertion (A) : In the process of nuclear fission, the amount of nuclear energy generated by the fission of an atom of uranium is so tremendous that it produces 10 million times the energy produced by the combustion of an atom of carbon from coal. Reason (R) : The nucleus of a heavy atom such as uranium, when bombarded with low energy neutrons, splits apart into lighter nuclei. The mass difference between the original nucleus and the product nuclei gets converted to tremendous energy?
Year of Question :(2012)

• (a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A)
• (b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A)
• (c) (A) is true, but (R) is false
• (d) (A) is false, but (R) is true. (2020)

Answer:

• (a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A). Answer question numbers 21-24 on the basis of your understanding of the following paragraph and the related studied concepts : Geothermal energy is the energy produced by the heat of molten rocks formed in the deeper hot regions of the earths crust
• This energy is harnessed to generate electricity. When water is made to flow deep underground in the rocks it returns as steam (or hot water, which is later converted to steam) to drive a turbine on an electric power generator. In India, exploration and study of geothermal fields started in 1970. The Geological Survey in India has identified 350 geothermal energy locations in the country. The most promising of these is in Puga valley of Ladakh. The estimated potential for geothermal energy in India is about 10000 MW. There are seven geothermal provinces in India namely the Himalayas, Sohna, West coast, Cambay, Son-Narmada-Tapi; Godavari and Mahanadi. Most power station in India produce Alternating Current (AC). (2020)

Question 21.
What are geothermal energy hot-spots?
Year of Question :(2012)

Answer: Due to geological changes, molten rocks formed in the deeper hot regions of earths crust are pushed upward and trapped in certain regions. These regions are called hot spots

Question 22.
Name two countries, other than India, where power plants based on geothermal energy are operational?
Year of Question :(2011)

Answer: Many geothermal power plants are operational in countries such as New Zealand and United States of America

Question 23.
Name the phenomenon that explains the working of an electric generator?
Year of Question :(2012)

Answer: An electric generator works based on the principal of electromagnetic induction

Question 24.
State an important advantage of using AC over DC?
Year of Question :(2012)

Answer: A.C. can be transmitted to distant places without much loss of electric power than D.C.

Question 25.
Name any one material used to make a solar cell and also mention the range of voltage produced by a typical cell?
Year of Question :(2017)

Answer: Silicon is used to make a solar cell. A typical cell develops a voltage of 0.5 - 1 V

Question 26.
Write the name of the substance whose vapours are used to run the turbine of the generator of ocean thermal energy plant?
Year of Question :(2015)

Answer: Volatile liquid ammonia

Question 27.
Name the energy obtained from sea or ocean water due to the difference in temperature at the surface and in deeper sections of these water bodies?
Year of Question :(2015)

Answer: Ocean thermal energy

Question 28.
Explain the term Hot Spots in the context of geothermal energy production?
Year of Question :(2013)

Answer: Due to geological changes, molten rocks formed in the deeper hot regions of earths crust are pushed upward and trapped in certain regions. These regions are called hot spots

Question 29.
Name any two elements that are used in fabricating solar cells. ?
Year of Question :(2013)

Answer: Silicon, Silver

Question 30.
Differentiate between energy obtained by burning fossil fuels and that obtained as solar energy?
Year of Question :(2013)

Answer:

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• The reserves of fossil fuels are limited, i.e., exhaustible whereas solar energy is available in abundance (and that too without any cost), i.e., it is inexhaustible
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• Fossil fuels cause pollution on burning whereas solar energy is pollution free
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• Fossil fuels can provide energy at any required time whereas solar energy becomes unavailable when the sky is covered with clouds
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Question 31.
Define the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor?
Year of Question :(2016)

Answer: The phenomenon of splitting up of a heavy nucleus, on bombardment with slow speed neutrons, into two fragments of comparable mass, with the release of two or more fast moving neutrons and a large amount of energy is known as nuclear fission. Steps involved in generating electricity

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• Large atoms like uranium or plutonium are bombarded by slow moving neutron
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• Large atoms break and releases lots of heat energy
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• This heat is used to boil water to steam
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• This steam rotates the turbine which produces electricity

Question 32.
Name the three forms in which energy from sea is available for our use and write one limitation of each?
Year of Question :(2016)

Answer:

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• Tidal Energy: Limitation : The rise and fall of water during tides is not high enough to generate electrical energy on a large scale. There are very few places suitable for building dams. It is for these reasons, the tidal energy is not likely to be a major source of energy
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• Wave energy Limitation : Wave energy would be a viable proposition only where waves are very strong
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• Ocean thermal energy Limitation : The efficient commercial exploitation is difficult

Question 33.
Nuclear power is an excellent non-conventional source of energy. Still it is not used commonly for power generation. Why? State three reasons?
Year of Question :(2015)

Answer: Nuclear power can not be exploited easily because

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• the waste products of nuclear reactions (produced at nuclear power plants) are radioactive which keep on emitting harmful nuclear radiations for thousands of years. So, it is very difficult to store or dispose off nuclear wastes safely. Improper nuclear waste storage or disposal can pollute the environment
?
• there is the risk of accidents in nuclear reactors (especially the old nuclear reactors). Such accidents lead to the leakage of radioactive materials which can cause serious damage to the plants, animals (including human beings) and the environment
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• the high cost of installation of nuclear power plants and the limited availability of uranium fuel make the large scale use of nuclear energy prohibitive

Question 34.
Explain the principle and process of converting ocean thermal energy into electricity?
Year of Question :(2014)

Answer: Principle : There is a temperature difference between the water at the surface of the sea and deep below the sea. The difference in temperature at many places is of the order of 20°C. This difference in temperature can be exploited to produce electric energy in ocean thermal energy conversion plant (OTEC). Working : In one of the methods, a low melting point liquid or fluid such as ammonia (volatile liquid) or chlorofluorocarbon (CFC) is used to run the turbine of a generator. The warm surface water is used to boil the liquid like ammonia or CFC in a heat exchanger and vapours thus formed are used to drive the turbine of the generator. In another exchanger cold water from the depth of the ocean is pumped up to condense the vapours of the ammonia again to liquid. This ammonia is reused and the cycle repeats

Question 35.
Give two examples each of the following?
Year of Question :(2011)

• (i) Renewable sources of energy
• (ii) Non-renewable sources of energy (AI 2011)

Answer:

• (i) Examples of renewable sources of energy are wind energy, solar energy, etc
• (ii) Coal, petroleum and natural gas are the examples of non-renewable sources of energy

Question 36.
Write two points of difference between renewable and non-renewable sources of energy. Give one example of each?
Year of Question :(2017)

Answer:

Question37.
Name any two fossil fuels?
Year of Question :(2012)

Answer:A good fuel is the one which

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•  has high calorific value
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•  is non-polluting
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•  is easy to transport and easily available
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•  has moderate ignition temperature
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Question38.
Mention the purpose of blackening the interior of a solar cooker?
Year of Question :(2014)

Answer:The purpose of blackening the interior of a solar cooker is that the black surface absorbs more heat radiations of incident solar energy (about 98%) as compare to white or other light coloured surface

Question39.
Why do people oppose the construction of Tehri Dam on the river Ganga and Sardar sarover project on the river Narmada.  (Or) Mention three disadvantage of producing hydroelectricity by constructing the dams.(Or) List any three ways in which construction of dams for production of electricity adversely affects the environment of that place?
Year of Question :(2012)

Answer:

• 1.Large area is required to build the dam that  result rehabilitation of displaced people
• 2.Large eco-systems are destroyed when submerged under the water in dams
• 3.The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane gas which leads to a green-house effect

Question40.
Reenas father works with a company that builds dams. Once he took her to the site where a dam was being built. Reena saw a group of people sitting there and shouting slogans against the building of dam. She talked the group of people and asked them about their problems and then discussed it with her father. She then tried to convince the people to talk with the authorities and come to an amicable solution. The discussion was successful. Reenas father was very proud of his daughter. Now answer the following questions?
Year of Question :(2015)

• (i) Why was Reenas father proud of his daughter
• (ii)Why was the group of people protesting against the building of dam
• (iii) Reenas contribution to the peaceful resolution of the conflict proved to boon for many citizens of the country. How

Answer:

• (i) Because she convinced the people by explaining them the advantage of constructing dam and come with a solution of rehabilitation of displaced peoples. So the contribution to the peaceful resolution of the conflict make Reenas father proud of his daughter
• (ii)The group of people protesting against the building of dam because of following disadvantages
• (a) A large area of agricultural land and human habitation are sacrificed as it get submerged at the dam site
• (b) Large ecosystems are destroyed when submerged under water
• (c) The decomposition of vegetation under anaerobic condition produces methane gas which is also a greenhouse gas
• (iii)(a) The citizens are not affected by flood as it can be controlled by storing the water behind the dam
• (b) Farmers get benefited as water for irrigation is available for the whole year
• (c) Low cost of production of electricity gives monetary gain which is a boon to citizens

Question41.
Bio gas is an excellent fuel. Justify the statement by giving two reasons. Mention the main constituents of bio gas along with its percentage?
Year of Question :(2012)

Answer:

• (i) It burns without smoke and leave no residue therefore causes no atmospheric pollution
• (ii)Its heating capacity is high, i.e. it has high calorific value. Main constituents of bio gas: The composition of bio gas varies depending upon the nature of organic matter feeding inthe digester and advanced waste treatment technology. The typical composition of bio gas is Methane                                50 - 75% Carbon dioxide                     25 - 50% Nitrogen                                   0 - 10% Hydrogen                                 0 - 1% Hydrogen sulphide                0 - 3%

Question42.

• (a)Define tidal energy
• (b)Explain how the tidal energy is harnessed and write one limitation of the use of tidal energy

Answer:

• (a) Tidal energy: The energy produced by the surge of ocean water during high and low tides due to difference in sea-levels is called tidal energy. The high and low tides occur due to the gravitational pull of the moon. This causes enormous movement of water
• (b) Tidal energy is harnessed by constructing a dam near the shores. During the high tides water flows into the dam and during the low tides, water flows out. This flowing water rotates the turbine, present at the opening of the dam and produces electricity

Question43.
Define process of nuclear fission. Writ the steps involved in generating electricity in a nuclear reactor?
Year of Question :(2012)

Answer:Nuclear Fission: The process in which a heavy nucleus (such as uranium, plutonium or thorium) is broken into two nearly equal fragments when bombarded with low-energy neutrons and a tremendous amount of energy is released. This process is called nuclear fission

Steps involved in generating electricity:
• 1.The fuel rods full of uranium pellets are placed in a nuclear reactor chamber
• 2.Low-energy neutrons are bombarded on uranium fuel rod.
• 3. A self-sustaining fission chain reaction starts that releases energy at a controlled rate
• 4.With this heat the reactor converts water to steam at a high temperature and pressure
• 5.This high temperature and pressure steam spins generator turbines producing electricity
• 6.The steam cools back into water, which can then be used over again

Important Questions and Answers from Chapter 14: Sources of Energy

Question 1.
What are the characteristics of a good source of energy?

Answer:
A good source of energy should:
Release a large amount of energy per unit mass or volume.
Be easily accessible and affordable.
Be easy to store and transport.
Cause minimal pollution or harm to the environment.
Be efficient for the intended task, like cooking or generating electricity.


Question 2.
What are fossil fuels? Explain their disadvantages.

Answer:
Fossil fuels include coal, petroleum, and natural gas.
They are formed from dead plants and animals over millions of years.
Disadvantages:
Non-renewable: They will eventually run out as they take millions of years to form.
Pollution: Burning fossil fuels produces harmful gases like carbon dioxide, leading to global warming and acid rain.
Environmental impact: Extracting and using fossil fuels damages ecosystems and causes air pollution.


Question 3.
Why are we exploring alternative sources of energy?

Answer:
Fossil fuels are limited and will be exhausted in the future.
Their use leads to air pollution and contributes to climate change.
Alternative energy sources like solar energy, wind energy, and hydroelectric power are renewable and cleaner.
As technology improves, renewable energy becomes more cost-effective and efficient.


Question 4.
What is hydroelectric power, and what are its advantages and disadvantages?

Answer:
Hydroelectric power: Electricity generated by using the energy of falling water, usually from dams.
Advantages:
Renewable: It uses water, which is replenished by rain.
Pollution-free: It does not emit harmful gases or cause air pollution.
Reliable: Dams can generate electricity consistently, especially during rainy seasons.
Disadvantages:
Limited locations: Dams can only be built in certain areas, usually in hilly regions.
Environmental damage: Building dams can flood large areas, displacing people and wildlife.
Methane emissions: Decomposing vegetation in reservoirs can produce methane, a greenhouse gas.


Question 5.
What is wind energy? What are its limitations?

Answer:
Wind energy: Energy generated by converting the kinetic energy of wind into electricity using wind turbines.
Advantages:
Renewable: Wind is an endless resource.
Clean: Wind energy does not produce harmful emissions or pollution.
Limitations:
Inconsistent: Wind does not blow all the time, so wind farms may not generate electricity continuously.
Requires large space: Wind farms need vast areas of land.
High initial cost: The setup and maintenance of wind turbines are expensive.


Question 6.
What is solar energy, and how is it used?

Answer:
Solar energy: Energy harnessed from the Sun’s radiation.
Uses:
Solar cookers: Use sunlight to cook food.
Solar heaters: Use solar energy to heat water.
Solar cells: Convert sunlight into electricity. These cells are arranged in solar panels to produce enough electricity for practical use.
Advantages:
Renewable: The Sun is a constant and inexhaustible source of energy.
Environmentally friendly: Solar energy does not cause pollution.
Limitations:
Dependence on sunlight: Solar devices work only during the day and are less effective on cloudy days.
High cost: Installing solar panels can be expensive.


Question 7.
What is nuclear energy? What are its benefits and risks?

Answer:
Nuclear energy: Energy generated by splitting the nucleus of an atom in a process called nuclear fission.
Benefits:
Large energy output: A small amount of nuclear fuel can produce a massive amount of energy.
Efficient: Nuclear power plants generate a lot of electricity.
Risks:
Radioactive waste: The disposal of nuclear waste is hazardous and can harm the environment.
Accidents: Nuclear plant accidents, like Chernobyl (1986), can release dangerous radiation.
High cost: Building and maintaining nuclear plants is expensive.


Question 8.
What are the environmental consequences of using energy sources?

Answer:
Using energy sources impacts the environment:
Fossil fuels cause air pollution, global warming, and acid rain.
Hydroelectric dams can lead to the loss of land and displacement of people.
Wind energy requires large land areas, and wind turbines may affect local wildlife.
Solar energy is clean but depends on the production of solar panels, which may involve pollution.
Conclusion: No energy source is completely free of environmental impact, but some are cleaner than others.


Question 9.
What are renewable and non-renewable energy sources? Give examples.

Answer:
Renewable sources:
Energy sources that can be replenished naturally.
Examples: Solar energy, wind energy, hydroelectric power, and biomass.
Non-renewable sources:
Energy sources that cannot be replaced once used.
Examples: Fossil fuels (coal, petroleum), nuclear energy.


Question 10.
What are the advantages and disadvantages of using a solar cooker?

Answer:
Advantages:
No pollution: Solar cookers do not produce smoke or harmful gases.
Free energy: Sunlight is free and abundant in many parts of the world.
Disadvantages:
Weather-dependent: Solar cookers only work when there is enough sunlight.
Slow cooking: Cooking with a solar cooker may take longer than with conventional methods.

• CBSE Class 10 SA-1 Science Set 1 QP
• CBSE Class 10 Science Source of Energy Notes