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Page No 253: - Chapter 14 Sources & Energy class 10 ncert solutions Science - SaraNextGen [2024]


Question 1:

What kind of mirror − concave, convex or plain − would be best suited for use in a solar cooker? Why?

Answer:

A solar cooker uses heat of the sunlight to cook and heat food. A mirror is used in order to reflect and focus sunlight at a point. A concave mirror is used in a solar cooker for this purpose. The mirror focuses all the incident sunlight at a point. The temperature at that point increases, thereby cooking and heating the food placed at that point.

Question 1:

Can any source of energy be pollution-free? Why or why not?

Answer:

No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly.

Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.

Question 2:

What are the limitations of the energy that can be obtained from the oceans?

Answer:

The forms of energy that can be obtained from the ocean are tidal energy, wave energy, and ocean thermal energy. There are several limitations in order to harness these energies.

(i) Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.

(ii) High dams are required to be built to convert tidal energy into electricity.

(iii) Very strong waves are required to obtain electricity from wave energy.

(iv) To harness ocean thermal energy efficiently, the difference in the temperature of surface water (hot) and the water at depth (cold) must be 20ºC or more.

Question 2:

Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

Answer:

Hydrogengas is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG. On the other hand, hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Hence, hydrogen is cleaner than CNG.

Question 3:

What is geothermal energy?

Answer:

Geothermal power plants use heat of the Earth to generate electricity. This heat energy of the Earth is known as geothermal energy.

When there are geological changes, the molten rocks present in the core of the earth are pushed to the earth’s crust. This forms regions of hot spot. Steam is generated when the underground water comes in contact with these hot spots forming hot springs. This trapped steam is used to generate electricity in the geothermal power plants.

Question 4:

What are the advantages of nuclear energy?

Answer:

The advantages of nuclear energy are as follows:

(a) Large amount of energy is produced per unit mass.

(b) It does not produce smoke. It is a clean energy.

(c) Fission of one atom of uranium produces 10 million times the energy released by burning of one atom of carbon.

(d) Fusion of four hydrogen atoms produces huge amount of energy approximately equal to 27 MeV.

Also Read : Page-No-254:-Chapter-14-Sources-&-Energy-class-10-ncert-solutions-Science

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