CBSE Class 10 Science Chapter-14 Sources of Energy – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 10 Science Chapter 14 – Sources of Energy prepared by expert Science teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 10 Science Chapter-14 Sources of Energy Important Questions
CBSE Class 10 science Important Questions Chapter 14 – Sources of Energy
3 Mark Questions
1. (a) Distinguish between renewable and non- renewable sources of energy?
(b) Choose the renewable source of energy from the following list: coal, biogas, sun, natural gas.
Ans.(a) Difference between renewable and non-renewable sources:
(b) Biogas and the sun are renewable sources of energy.
2. (a) Name the device used to convert
(i) Solar energy in to heat and
(ii) solar energy in to electricity.
(b) Explain the working of windmill
Ans.(a) (i) Solar cooker
ii)Solar cell.
(b)When the wind blows with a minimum speed of 15km/hr, the kinetic energy of the wind is used to rotate the blades of wind mill. The rotation energy of the blades is used to rotate the armature of the generator and generator in turn produce electricity.
3. What is biogas? How can biogas be obtained? Why the use of biogas obtained from cow dung is advised to use as compared to cow dung cakes?
Ans. Biogas is a mixture of gases namely methane,
. it is obtained from an aerobic decomposition of cow dung and plants and animal wastes in a biogas plants. Biogas is advised for burning in preference to burning of cow- dung cakes because:
(i) it cause no air pollution
(ii) It is a cheaper source of energy.
4. What are the limitations of extracting energy from
(a) the wind
(b) waves
(c) tides
Ans.(a) Wind energy is not sufficient to operate heavy machines and moreover it is limited to a certain place.
(b)Energy of the waves can be extracted only if strong wind blows all the time across the sea.
(c)Tidal power plant can extract the tidal energy from the water levels of high tide and low tide is very large.
5. Name three forms in which energy from ocean is made available for use. What are OTEC power plants? How do they operate?
Ans. (i) Muscular energy to perform different activities like taking bath, climbing stairs and muscular energy comes from food we eat.
(ii) Fossil fuel energy used in bus or car to reach the school and this energy come from fossil fuels like petrol, diesel and CNG.
(iii)Chemical energy in the form of breakfast and it also comes from the food we eat.
6. List three forms of energy we use when we wake up from morning till we reach the school. Also from where do we get these different forms of energy?
Ans. (i) Tidal energy
(ii) Ocean waves energy
(iii) Ocean thermal energy
OTEC power plants are ocean thermal energy conversion plants. For operating OTEC temperature difference of 
or more between the surface water of ocean and inside water of ocean is required to boil liquid like ammonia or chlorofluorocarbon (CFC). The vapors of the liquid at high pressure used to rotate the turbine of the generator to produce electricity.
7. Compare and contrast bio- mass and hydro-electricity as source of energy. The production cost of hydroelectricity is cheaper than the electricity produced in a thermal power station. Explain why?
Ans.
In a thermal power station coal is burnt to produce electricity whereas hydroelectricity is produced by allowing the water to fall on turbines. Water in rivers is available free of cost but the cost of extracting and transporting coal is very high.
8. What kind of mirror concave, convex or plane would be best suited for the use in a solar cooker. Why? What is the role of glass sheet used in a solar cooker? Also write two disadvantages of using a solar cooker?
Ans. Concave mirror will be best suited for the use in solar cooker because it concentrates all the sunlight to a point after reflection from the mirror and thus raises the temperature of that point.
Plane glass plate does not allow the infrared or heat radiation entered in the box to go outside the box thus heating the box and creating greenhouse effect.
The two disadvantages of using a solar cooker are:
(i)Food cannot be cooked at night and on a cloudy day by using a solar cooker.
(ii)Food cannot be cooked quickly by using a solar cooker.
9.What is a good source of energy?
Ans. A good source of energy should have the following qualities:
(a) It should be easily available.
(b) It should have high calorific value.
(c) It should be easy to store and transport
(d) It should be economical
(e) It should not cause environmental pollution.
10. What are the disadvantages of fossil fuels?
Ans. There are following disadvantage of fossil fuels:
(a) Burning of fossil fuels causes’ pollution.
(b) Oxides of Sulpher and nitrogen produced on burning of fossil fuel causes acid rain.
(c) Carbon dioxide causes greenhouse effect.
(d) Fossil fuels are non-renewable sources of energy.
11. Why are we looking at alternate sources of energy?
Ans. Fossil fuels are non-renewable sources of energy and their reserves are limited one. Hence, we need to conserve them. If we continue consuming these sources at same rate as presently, we may soon run out of energy. To avoid such a situation we are looking for alternative sources of energy.
12. How has the traditional use of wind and water energy been modified for our convenience?
Ans. To use energy of flowing water large dams are built in hilly regions to store huge amount of water at a height. This water is used to produce hydroelectricity. Wind energy is used to generate electricity by using windmill that converts the wind energy into electricity.
13. What are limitations of the energy that can be obtained from the oceans?
Ans. Limitations of energy obtained from oceans:
(a) There are very few locations where dams to utilize tidal energy can be built.
(b) Cost of installation of power houses is extremely high and efficiency of plants is comparatively small.
(c) Power plants built in oceans will need high continuous maintenance.
14. What is geothermal energy?
Ans. Geothermal energy is the heat energy present inside the earth in certain regions called hot spots. When underground water comes in contact with the hot spot, steam is generated. This steam is routed through a pipe to a turbine and used to generate electricity.
15. What are the advantages of nuclear energy?
Ans. Geothermal energy is the heat energy present inside the earth in certain regions called hot spots. When underground water comes in contact with the hot spot, steam is generated. This steam is routed through a pipe to a turbine and used to generate electricity.
16. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Ans. Solar energy, wind energy, ocean energy etc. are renewable sources of energy due to the following reasons:
(a) These forms of energy are available in plenty in our natural environment.
(b) These energy sources will not be depleted because their supply is large and extraction of usable energy from these sources is negligible.
17. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Ans. Coal and petroleum are two exhaustible sources of energy. These fuels were formed over million for years ago and there are only limited reserves. If we continue to use them as at present, these reserves will be exhausted soon.
18. Compare and contrast fossils fuels and the Sun as direct sources of energy.
Ans. Distinction between fossils fuels and Sun energy:
19. Compare and contrast bio-mass and hydroelectricity as sources of energy.
Ans. Difference between bio-mass and hydroelectricity:
20. What are the qualities of an ideal source of energy?
Ans. The qualities of ideal sources of energy are:
(a)It should be easily accessible, inexhaustible and a renewable source of energy and cost of harnessing energy should be reasonably small.
(b)It should be easily stored and transported.
(c)It should have high calorific value.
(d)It should be pollution free.
21. 
has been used as a rocket fuel. Would you consider it as a cleaner fuel than CNG? Why or why not?
Ans.H when burnt in presence of 02 produces 1120 as the only product with release of lot of heat energy. Water does not cause any damage to environment while CNG during burning produces CO and water. CO is not a pollutant yet it leads to rise in the temperature (global warming), this rise is called greenhouse effect and this will affect polar ice, and life on the earth is at risk. Thus, 1 is a cleaner fuel than CNG.
22. Why is biogas a better fuel than animal dung-cakes.
Ans. Biogas is a better fuel than animal dung-cakes because-
(a) Burning of animal dung-cakes produces lot of pollution whereas biogas is a smokeless fuel.
(b) The calorific value of Biogas is much higher than that of animal dung-cakes.
(c) Animal dung cakes leaves residue after burning whereas biogas leaves no residue.
23. How difference in temperature helps to harness energy from ocean?
Ans. The difference in temperature helps to obtain energy in ocean- thermal — energy conservation plants, which operate for temperature difference of 200 C or more. The warm surface water is used to boil a volatile liquid. The vapour of the liquid are used to run the turbine of generator, the cold water from the depth of the ocean is pumped up and condense vapour again to liquid.
24. Write three reasons why construction of Tehri Dam on river Ganga and Sardar Sarovar project on river Narmada is opposed by local people and environmentalist?
Ans. (i) Rehabilitation problems, loss of agricultural land.
(ii)Disturbance of ecological balance.
(iii) Forming of greenhouse gases due to decomposition of plant in water.
25. Write three environmental consequences of the various source of energy we used?
Ans. Greenhouse effect, improper use of natural resources, pollution.
