NCERT Solutions for Class 10 Science Chapter 14

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NCERT Solutions for Class 10 Science Chapter 14

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Class X Science – Sources of Energy

Important Questions with Answers for CBSE Exams – 2019

Question 1:
What is meant by a source of energy? OR What are the factors that should be taken into consideration for selecting a source of energy? List any three.
Answer 1:
We need energy to perform various functions of life. The materials that provide the requisite amount of energy is the source of energy. For example,
(i) We need heat energy to cook food. The various sources are: Fuels, wood, coal, kerosene, cooking gas etc.
(ii) We need energy for our transport. The various sources are: petrol, diesel.
(iii) We need energy to light bulbs, tubes, to run radio, television and other power appliances. The source is electricity.
(iv) Production in factories and agriculture also need energy. The source is diesel and electricity.

Question 2:
What is geothermal energy?
Answer 2:
The interior or deeper regions of earth’s crust are very hot. The temperature is so high that even rocks melts. If this heat is utilized as a source of energy, it is called geothermal energy.

Question 3:
Differentiate between renewable and non-renewable source of energy with one example for each.
Answer 3:
(i) Non-renewable sources: Fossil fuels like coal, petroleum and natural gas are non-renewable energy sources. These are produced over millions of years due to slow changes and under special circumstances. These are not continuous processes and further it is not becoming possible to discover their new deposits. With the present rate of their consumption, it is estimated that known deposits of petroleum in our country will be exhausted in another 200 years and that of coal may last for another 250 years.
(ii) Renewable sources: The energy derived from flowing water, wind, tides, ocean waves and bio-gas are the renewable sources. These sources can be harnessed into energy so long as the earth derives its heat and light from the sun or so long as the present solar system exists. Nuclear energy and geothermal energy is also likely to be available for a much longer time. Wood is another renewable source of energy. Though it takes almost 15 years for a tree to mature, this and nuclear energy are also classified as renewable sources.

Question 4:
What are the two disadvantages of burning fossil fuels? OR State with reason three disadvantages of using fossil fuels.
Answer 4:
(i) Burning of coal and petroleum lead to air pollution.
(ii) They cause acid-rain by forming oxides of carbon, nitrogen and sulphur. This affects our water and soil sources.
(iii) Burning of fossil fuels cause smog which causes breathing problems and other hazards.


More Questions for Exams

Question 1:
Why is bio-gas considered an ideal fuel for domestic use? OR Bio-gas is an excellent fuel. List three reasons to justify this statement.
Answer 1:
Bio-gas is considered a good domestic fuel because of the following reasons:
(i) Bio-gas burns without any smoke and so does not cause air pollution.
(ii) Bio-gas produces a large amount of heat per unit mass and thus has high calorific value.
(iii) Bio-gas does not leave any residue on burning and is thus a clean fuel.
(iv) Bio-gas does not cause any storage problem. It can be continuously supplied by the pipes directly from the gas plant.
(v) The production of bio-gas does not involve any running cost and is cheaper than most common fuels.

Question 2:
What are fossil fuels?
Answer 2:
Coal, petroleum and natural gas are examples of fossil fuels. These are found in nature due to the decomposition of animals and plants which have remained embedded inside earth’s crust due to geological changes over millions of years.

Question 3:
What are wind energy farms?
Answer 3:
The rotatory motion of the windmill can be utilized to rotate the armature of an electric generator in order to produce electricity. However, the electricity produced by a single windmill is quite small and thus cannot be used for commercial purpose. Therefore, a number of windmills are erected over a large area. The energy output of each windmill is coupled. This is called wind energy farms. The most essential condition for creating wind energy farms is to locate an area where wind blows for greater part of the year at a speed of about 15 km/h.

Question 4:
Out of two solar cooker, one was covered by a plane glass slab and the other was left open. Which of the two solar cookers will be more effective and why?
Answer 4:
The solar cooker covered with glass slab will be more efficient because the heat rays trapped in its will not be able to escape easily. Thus, the heating in this case will be better.


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