Sources of Energy Class 10 Important Questions and Answers
Important Questions for Class 10 Science Chapter 14 Sources of Energy covers each topic of the chapter. These questions aim at providing a better understanding of the chapter to the students and can be downloaded in PDF format. These important question bank help students in clearing their doubts so that they can score well in the exam.
While preparing for exams, students should practise these important questions of Class 10 Science to understand the concepts better. Solving important questions of Class 10 Science Chapter 14 will teach students time management skills and enhance their problem-solving skills. Also, students may come across a few of these questions in the board exam.
Important Questions for Class 10 Science Chapter 14 – PDF
1. Name any two elements that are used in fabricating solar cells.
Answer: Silicon and gallium.
2.What are solar cells? Explain the structure of solar panel. List two principal advantages associated with solar cells.
Answer: A solar cell is a device which converts solar energy directly into electricity.
Construction: The box of the solar cooker is made of non-conducting material e.g., plastic or fibre glass with thick inner walls. These walls are painted in black. A plane mirror is hinged on the top so that it reflects sunlight into the box.
Working: The purpose of the box is to increase the effective area for collection of solar energy.
Whole box is covered with glass sheets. These glass sheets prevent the loss of longer
wavelength infrared radiation from inside the box to outside.
Within two to three hours, the temperature inside rises to about 140 °C.
3. ‘Bio-gas is an excellent fuel’. List four reasons to justify this statement.
Write the main constituent of this gas and state its percentage.
Answer: (i) The four gases commonly present in bio-gas are methane, carbon dioxide, hydrogen and hydrogen sulphide.
(ii) Main advantages of using bio-gas over fossil fuels are as given below :
(1) Bio-gas is an excellent fuel as it contains upto 75% methane which burns without smoke.
(2) Bio-gas bums completely and leaves no residue i.e., ash.
(3) Bio-gas is a renewable, convenient and efficient source of energy, whose heating capacity is high.
(4) It gives us a safe method to dispose off wastes like animal dung, human excreta and other bio-wastes.
4. Name any two nutrients that the spent slurry has in a bio-gas plant.
Answer: Nitrogen and phosphorous are two nutrients present in the spent slurry.
5. Why is bio-gas considered an excellent fuel?
Answer: Bio-gas is an excellent fuel because it bums without smoke, leaves no residue ash and its heating capacity is high.
6. What is a dam? Why do we seek to build large dams? While building large dams, which three main problems should particularly be addressed to maintain peace among local people? Mention them.
Answer: A dam is a huge construction being done to obstruct the river flow at the place. As a result a large artificial lake is created there which can be used to store water.
We want to build large dams so as to store large amount of water, which can then be used to produce electricity by means of a hydropower plant.
While building large dams, following three main problems should particularly be addressed to maintain peace among local people :
(i) Construction of dam involves submergence of large areas of agricultural and forest land and human habitation.
(ii) Large eco systems are destroyed.
(iii) Problem of satisfactory rehabilitation of displaced people is a major problem.
7. Write the energy conversion that takes place in a hydropower plant.
Answer: The energy transformation taking place at hydropower plants is shown below:
8. Name two constituents of biogas.
Answer: Methane CH4, Hydrogen H2, carbon dioxide C02, hydrogen sulphide H2S.
9. What is biogas?
Answer: Biogas is mixture of methane, carbon-dioxide, hydrogen and hydrogen sulphide.
10. Write the percentage of methane in bio-gas.
Answer: 75% of bio-gas is methane.
11. Mention three ways to reduce the pollution caused by fossil fuels.
Answer: Three possible ways to reduce the pollution caused by fossil fuels are :
(i) Increase the efficiency of the combustion process.
(ii) Adequate techniques must be employed so as to reduce the escape of harmful gases and ash into the surroundings.
(iii) The fossil fuel may be used to generate electricity, which can then be conveniently used in homes and industry.
12. Explain the term ‘tidal energy’. How is electricity produced from tidal energy?
Answer: Tidal energy is the kinetic energy possessed by the rising and falling water in seas and oceans during high and low tides respectively. To harness tidal energy, a dam is constructed across a narrow opening to the sea. The water moves in and out of the openings in the dam during high and low tides. As the water moves through the openings, it flows over the turbines fixed inside the dam that generate electricity.
13. (i) Name the four gases commonly present in bio-gas.
(ii) List two advantages of using bio-gas over fossil fuels.
Answer: (i) The four gases commonly present in bio-gas are methane, carbon dioxide, hydrogen and hydrogen sulphide.
(ii) Main advantages of using bio-gas over fossil fuels are as given below :
(1) Bio-gas is an excellent fuel as it contains upto 75% methane which burns without smoke.
(2) Bio-gas bums completely and leaves no residue i.e., ash.
(3) Bio-gas is a renewable, convenient and efficient source of energy, whose heating capacity is high.
(4) It gives us a safe method to dispose off wastes like animal dung, human excreta and other bio-wastes.
14. Define process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor.
OR
Define nuclear fission. Write the steps involved in generating electricity in a nuclear reactor.
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:
(i) Fuel rods full of uranium pellets are placed in a nuclear reactor chamber.
(ii) Low-energy neutrons are bombarded on uranium fuel rod.
(iii) A self-sustaining fission chain reaction starts that releases energy at a controlled rate
(iv) With this heat the reactor converts water to steam at a high temperature and pressure
(v) This high temperature and pressure steam spins generator turbines producing electricity.
(vi) The steam cools back into water, which can then be used over again.
15. Identify the part of a solar cooker that produces greenhouse effect.
Answer: The plane glass plate cover of a solar cooker produces greenhouse effect.
16. What is the minimum wind velocity required for obtaining electric power with a windmill generator?
Answer: 15 km h-1.
17. Name any two nuclear fuels used for the process of nuclear fission.
Answer: Uranium and plutonium.
18. (a) How charcoal is better fuel than wood? Why?
(b) How does bio-gas plant help to reduce the problem of pollution?
Answer: (a) Charcoal is a better fuel than wood because it bums without flames, is comparatively smokeless and has a higher heat generation efficiency.
(b) A bio-gas plant helps to reduce the problem of pollution by utilising waste bio-mass by producing bio-gas and manure.
19. (a) List in tabular form two major differences between renewable and non-renewable sources of energy. (b) Why fossil fuels are classified as non-renewable sources of energy?
Answer: (a)
| Renewable Sources of energy | Non-renewable sources of energy |
| These are the energy sources which are inexhaustible i.e., can be replenished and can be used to produce energy again and again. | These are the energy sources which are exhaustible i.e., cannot be replenished after being once consumed. |
| Solar energy, wind energy are renewable sources of energy. | Coal, Petroleum, natural gas and wood are non-renewable sources of energy. |
(b) Fossil fuels were formed due to certain very slow changes occurring inside the earth under special circumstances spread over millions of years. Since these conditions are not prevailing now, it is not possible to replenish the amount of fossil fuels being consumed. Hence, these are classified as non-renewable sources of energy.
20. State any three limitations of harnessing nuclear energy.
Answer: Three main limitations of harnessing nuclear energy are as follows:
(i) The most important problem is the storage and disposal of spent or used fuel because it is highly radioactive. Improper nuclear waste storage and disposal may lead to environmental contamination.
(ii) There is a risk of accidental leakage of nuclear radiation from the nuclear reactor.
(iii) Cost of installation of a nuclear power plant is very high.
21. How is nuclear energy generated? State in brief the process of utilising this energy in the production of electricity. Mention the major hazard of nuclear power generation.
Answer: Nuclear energy is generated by the process of nuclear fission. The nucleus of a heavy atom such as uranium or plutonium, when bombarded with low energy neutrons, can be split apart into two lighter nuclei along with the release of tremendous amount of energy.
We design a nuclear reactor in which process of nuclear fission takes place at a sustained rate and energy is released at a uniform rate. This energy is utilised to convert water into steam, which then does work for rotating the turbine of electric generator. As a result, electricity is produced.
The major hazard of nuclear power generation is the storage and safe disposal of spent or used fuel so that no environmental contamination takes places.
22. Write one advantage of nuclear fission reaction.
Answer: In a nuclear fission reaction large amount of energy is released by a small quantity of nuclear fuel, which can be easily converted into electrical energy.
23. Mention the two factors that causes wind to blow.
Answer: Wind is caused by unequal heating of land mass and water bodies by solar radiation.
24. Define the process of “nuclear fission”.
Answer: Splitting up of a nucleus of uranium, when bombarded by neutrons, into two lighter nuclei along with release of a large amount of energy is called nuclear fission.
25. Explain, how does a hydro power plant produce electricity.
Answer: A hydro power plant converts the potential energy of stored water into electricity.
To produce hydro power electricity, a high rise dam is constructed at a suitable place on the river to obstruct the flow of water and there by collect water in a large sized reservoir. Due to rise of water level, the kinetic energy of flowing water is transformed into potential energy of stored water.
The water from the high level in the dam is carried through sluice gates and pipes to the turbine of electric generator, which is fitted at the bottom of the dam. Due to flowing water, turbine is rotated at a fast rate and electricity is produced.
26. (a) Define tidal energy.
(b) Explain how is tidal energy 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 puli of the moon. This causes enormous movement of water.
(b) Tidal energy is harnessed by constructing a dam near the shores. During high tides water flows into the dam and during low tides, water flows out. This flowing water rotates the turbine, present at the opening of dam and produces electricity.
Limitation of the use of tidal energy:
(i) The power output is variable, intermittent and is not on a large scale.
(ii) There are very few suitable sites that too with high installation cost of plant and its maintenance cost.
27. How can one say that Sun is the main source of energy on the earth?
Answer: Solar energy manifests itself in many forms through many processes both biological and physical. Plants utilise solar energy for photosynthesis. The solar energy trapped by land and water bodies brings about many physical changes resulting in wind, storm, ocean waves etc. Also fossil fuels e.g., coal, natural gas, petrol etc., have been formed due to very slow changes which occurred millions of years ago and were related to solar energy.
Energy of bio-gas etc., is also derived from solar energy.
28. Burning of fossil fuels causes lots of air pollution. Generally these fossil fuels are used in our vehicles.
(i) A s an aware citizen, list two ways to reduce air pollution caused due to vehicles.
(ii) Write two harmful effects other than air pollution, that are caused due to burning of fossil fuels.
Answer: (i) Two ways to reduce air pollution caused due to vehicles are as follows:
(a) The petrol used should be free of lead and sulphur impurities because oxides of these elements are toxic and cause much air pollution.
(b) Vehicles using diesel should be replaced by vehicles using CNG as a fuel.
(ii) Two harmful effects, other than air pollution, caused due to burning of fossil fuels are as follows :
(а) Burning of fossil fuels produce oxides of nitrogen and sulphur. These gases are acidic in nature and lead to acid rain which adversely affects our water and soil resources.
(b) Burning of fossil fuels produce carbon dioxide, which is a greenhouse gas and leads to global warming causing a lot of environmental and ecological problems.
29. State one limitation of solar energy available from solar cells.
Answer: Solar energy being a very good and renewable source of energy has some disadvantages also. Solar cells and their installation require a lot of money and therefore not many people can afford it. Also, they are weather dependent and cannot be used in rainy season or at the time of the year when sun is not visible.
30. What is the minimum wind velocity required to obtain useful energy with a windmill?
Answer: A windmill is a device (mill) that converts wind energy into electricity by using the blades of the windmill. The minimum velocity required by a windmill to obtain useful energy is 15 kilometers per hour.
31. Explain why is the solar cooker box covered with a plane glass plate?
Answer: The glass plate does not allow the heat to escape. This phenomenon is used in solar cookers as the solar cooker box is covered with a plane glass plate so as to capture more and more rays of the sun and allow maximum heating of the food placed in the box.
32. List any four areas where solar cells are being used as a source of energy.
Answer: Solar cells are the renewable source of energy which converts the solar energy (energy from the sun) into electricity. A few areas in which solar cells are used are as follows:
- Solar cells are used in traffic lights and street lights.
- Nowadays solar panels are also used in trains like metros.
- Food can be cooked using solar cookers.
- Some calculators also have solar cells embedded in them.
33. Write two advantages of classifying energy sources as renewable and non-renewable.
Answer: By classifying sources of energy as renewable and non-renewable:
- We can have a knowledge of how many sources are left and the proper ways they can be used so that we can pass them to our future generations.
- We can look for different alternates of the fast depleting non-renewable resources of energy.
34. (a) Classify the two fuels – CNG and hydrogen – as renewable and non-renewable.
(b) Justify the statement, “Hydrogen is a cleaner and better fuel than CNG”.
Answer: (a) CNG-compressed natural gas. It is a type of natural gas which is a non- renewable source of energy as it takes thousands of years to get replenished. Thus, CNG is a non-renewable source while hydrogen is a renewable source.
(b) Hydrogen is a much cleaner fuel than CNG because there is no hydrocarbon emission from hydrogen while CNG produces a lot of hydrocarbon emission which can cause pollution.
35. What is the importance of hydropower plants in India? Describe how electric energy is generated in such plants.
Answer: India is a country which is surrounded by water on three sides. This water is now used to generate electricity. Thus, hydropower plants are a good source of generating energy in India nowadays.
Generation of electric energy in hydropower plant:
Electricity production in a hydropower plant works on the principle that- energy always remains conserve and one form of energy can be converted into other.
Water from a great height is poured on a turbine with very great speed. This is done to convert the potential energy of water into its kinetic energy. When this water falls on turbine, it moves with very high speed thus converting this kinetic energy of water into electric energy.
36. A student constructed a box type solar cooker. He found that it is not working efficiently. What could this be due to? Give any four possible mistakes in the construction and operation of the solar cooker. What can maximum temperature ordinarily be reached inside a solar cooker?
Answer: There can be some basic mistakes which can be done by the student. Once the following mistakes are corrected, his/her solar cooker will start working efficiently-
(i) he/she might not have painted the cooker black. Black color is the best absorber of heat, thus painting it black will give better results.
(ii) he/she might not have covered the solar cooker with a glass cover. This glass cover traps the heat inside the cooker thus increasing the temperature.
(iii) while constructing a solar cooker one must place spherical reflectors inside the cooker so that they can converge the light at specific point thus giving a better result.
(iv) the sides of solar cooker must be covered with some thermally insulating layer to reduce the heat loss.
37. Name the three forms in which energy from oceans is made available for use. What are OTEC power plants? How do they operate?
Answer: The three forms in which energy from oceans is made available for use are:
- wave energy
- tidal energy
- thermal energy
OTEC- ocean thermal energy conversion plant.
Water present at the surface of sea is continuously being heated due to sunlight but, the water present in the deep-sea level is quite cold because sunlight is unable to penetrate deep into the water. So, this difference in the different levels of water in the sea can be utilized efficiently to create electricity. It is done in OTEC i.e., ocean thermal energy conversion plants.
38. Draw a labelled diagram of floating gas holder type biogas plant and describe it’s working. Mention any two advantage of using animal dung for making biogas over using it as a fuel in the form of dried dung cakes.
Answer: Biogas plant has a dome-shaped digester in which cow dung is kept. It is completely isolated and thus does not have oxygen in them. In this anaerobic conditions, methanogens (methane producing bacteria) perform their function & produces methane (CH4) by digesting the cow dung. Along with methane, carbon-dioxide (CO2), hydrogen sulphide (H2S) is also produced. These gases so produced is recovered from the gas outlet while the remaining slurry can be used as fertilizer.