Lesson: Sources of Energy

Question: 1

A solar water heater cannot be used to get hot water on:

(a) A sunny day

(b) A cloudy day

(d) A windy day

Solution:

Question: 2

Which of the following is not an example of a bio-mass energy source?

(a) Wood

(b) Gobar-gas

(d) Coal

Solution:

Question: 3

Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?

(a) Geothermal energy

(b) Wind energy

(d) Bio-mass

Solution:

Question: 4

Compare and contrast fossil fuels and the Sun as direct sources of energy.

Solution:

	Fossil fuels	Sun as direct source of energy
Source of energy	Remains of dead plants and animals	Sunlight reaching the earth
Availability	Limited	Unlimited
Cost	Costly	Available free of cost
Original Source	The sun is the original source of energy for fossil fuel.	Fusion reaction inside the sun

Question: 5

Compare and contrast bio-mass and hydroelectricity as sources of energy.

Solution:

	Bio-mass	Hydroelectricity
Main input/raw material	Wood, agricultural waste, animal refuse, etc.	Water
Availability	Limited	Limited
Production process	Simple for user	Need technical expertise
Energy source	Chemical energy stored in biomass	Potential energy of the stored water

Question: 6

What are the limitations of extracting energy from:

(a) The wind?

(b) Waves?

Solution:

(a) Wind energy: Limitations

(i) Extracting energy from windmill requires wind of speed more than 15 km/h to generate electricity.

(ii) A large number of windmills are required; a large area is required

(b) Waves: 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.

(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, moon, and the earth.

Question: 7

On what basis, would you classify energy sources as:

(a) Renewable and non-renewable?

(b) Exhaustible and inexhaustible?

Are the options given in (a) and (b) the same?

Solution:

(a) Renewable and non-renewable sources of energy:

The sources of energy that are continuously being produced in nature and are inexhaustible and renewable are known as renewable source of energy. Examples: The sun, wind, moving water, bio-mass, etc.

The sources of energy that are available in limited quantity, exhaustible and cannot be quickly replaced are known as non-renewable sources of energy.

Examples: Coal, petroleum, natural gas, etc.

(b) Exhaustible and inexhaustible source of energy:

Those sources of energy, which will deplete and exhaust after a certain period of time are called the exhaustible sources of energy.

Examples: Coal, petroleum, natural gas, etc.

The sources which will not exhaust in future and are unlimited are called inexhaustible resources of energy. Bio-mass is one of the inexhaustible sources of energy.

Examples: The sun, wind, moving water, bio-mass, etc.

Yes. The options given in (a) and (b) are the same.

Question: 8

What are the qualities of an ideal source of energy?

Solution:

An ideal source of energy is:

(a) Easily available.

(b) Easily accessible.

(d) Easy to store, use and transport.

(e) Inexhaustible.

(f) Able to produce huge amount of heat and energy on burning.

Question: 9

What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

Solution:

Advantages: A solar cooker uses sun’s energy which is an inexhaustible, pollution-free, renewable and free source of energy.

Disadvantages: A solar cooker is very expensive and works only when sufficient sunlight is available.

A solar cooker will have limited utility in places where sun is not visible for major part of the year.

Question: 10

What are the environmental consequences of the increasing demand for energy?

What steps would you suggest to reduce energy consumption?

Solution:

Consequences of increasing demand for energy:

(a) Exhaustion of energy resources

(b) Increase in pollution, greenhouse effect, acid rain

(d) Increased cost of getting resources as supply of energy would be limited

Some of the steps to reduce energy consumption are:

(a) Judicious use of sources of energy

(b) Afforestation

(d) Use of technology to tap resources like tidal energy, solar energy, thermal energy inside the earth and ocean, etc.

(e) Use of public transport system as and when possible, etc.