Lesson: Sources of Energy

Question: 1

What is a good source of energy?


An ideal source of energy is:

(a) Easily available.

(b) Easily accessible.

(c) Pollution free.

(d) Easy to store, use and transport.

(e) Inexhaustible.

(f) Able to produce huge amount of energy.

Question: 2

What is a good fuel?


A good fuel:

(a) Produces a huge amount of heat on burning.

(b) Does not produce a lot of smoke.

(c) Is easily available.

(d) Is less costly.

(e) Is renewable.

Question: 3

If you could use any source of energy for heating your food, which one would you use and why?


I would use natural gas as it is a non-polluting source of energy, easy to transport and produces huge amount of heat on burning.

Question: 4

What are the disadvantages of fossil fuels?


Apart from being exhaustible, the use of fossil fuels has the following environmental consequences.

Acid rain: Fossil fuels produce acidic gases like nitrogen dioxide and sulphur dioxide. These gases are responsible for acid rain.

Greenhouse effect: Burning of fossil fuels result in the release of large amount of carbon dioxide. This contributes to greenhouse effect.

Pollution: Burning of fossil fuels produce ash and/or smoke which adds to environmental pollution.

Question: 5

Why are we looking at alternate sources of energy?


Reasons for looking at alternate sources of energy:

(a) Use of traditional sources of energy has resulted in excessive pollution, global warming and acid rains.

(b) Traditional sources are mostly exhaustible.

(c) Alternate sources are renewable, pollution free and abundantly available.

Question: 6

How has the traditional use of wind and water energy been modified for our convenience?


Use of wind energy:

Earlier, wind energy was used to do mechanical work such as lifting/drawing water from a well. Now-a-days, they are used to generate electricity.

Use of water energy:

Earlier, water energy was used for transportation. Now-a-days, it is used to generate electricity.

Question: 7

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


A concave mirror can focus all the rays of the sun falling on it at a point. When a concave mirror is used, all the rays falling on the mirror are focused at a point. The temperature at that place increases. This helps in cooking food placed in a utensil at that place in the cooker.

Question: 8

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


We can obtain tidal energy, wave energy and ocean thermal energy from the oceans.

(a) Waves energy: Limitations

(i) Very strong ocean waves are required to extract energy from waves.

(ii) Currently the use of wave for energy generation is more of experimental in nature.

(b) Tidal energy: Limitations

(i) Very few viable sites are available where dams can be built for capturing tidal energy.

(ii) The occurrence of tides depends on the relative positions of the Sun, the Moon, and the Earth.

(c) Ocean thermal energy: Limitations

(i) The difference in the temperature of surface water (hot) and the water at depth (cold) in the ocean must be 20ÂșC or more for any viable use of this energy.

(ii) More technological advancement is required to fully tap this resource.

Question: 9

What is geothermal energy?


This heat energy from hot rocks present inside the earth is known as geothermal energy.

Question: 10

What are the advantages of nuclear energy?


The advantages of nuclear energy are that it:

(a) Releases of large amount of energy per unit mass of fuel used.

(b) Does not produce any smoke.

(c) Does not produce gases like carbon dioxide or sulphur dioxide; thereby does not contribute to the greenhouse effect or acid rain.

Question: 11

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


There are some sources like wind energy, solar energy, etc. that may appear to be pollution free, but practically no source of energy is pollution free as the use of any source directly or indirectly has some negative impact, however minimal it may be, on human beings and other living organisms.

Question: 12

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


CNG contains hydrocarbons and therefore, it has carbon contents and will lead to pollution.

On the other hand, the fusion of hydrogen does not produce any waste.

Hence, hydrogen is cleaner than CNG.

Question: 13

Name two energy sources that you would consider to be renewable. Give reasons for your choices.


Two renewable sources of energy are:

a) Sun: The sun has fuel to burn for billions of years. Therefore, it is considered to be a renewable source of energy.

b) Wind: Wind energy is due to the fast blowing air. The movement of wind is due to the uneven heating of the earth. This uneven heating of the earth will continue till we get the heat of the sun.

Question: 14

Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.


Two exhaustible energy sources are as follows:

a) Coal: There is limited quantity of coal available for us to use.

b) Wood: It is obtained by cutting down tree. We cannot continue to cut tree forever as cutting tree will have a negative impact on the existence of life on our planet. Hence, there is need to preserve trees.