Sources of energy Worksheet-5

Sources of energy Worksheet-5


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


  1. What are the advantages of nuclear energy?


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


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


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


  1. Compare fossil fuels and the Sun as sources of energy.


  1. Compare bio-mass and hydro-electricity as sources of energy.


  1. 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?


  1. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?


  1. What is a source of energy ?



  1. The energy obtained from the oceans and their limitations are :

(i) Tidal energy : Very few suitable sites are available for construction of dams and the power generation is intermittent and not very large.

(ii) Wave energy : Where power output is variable and the presently available technologies are very expensive.

(iii) Ocean thermal energy : Where the conversion efficiency is low (3% - 4%) and a lot of capital investment is required.


  1. 1. The mass of nuclear fuel (U-235) required is very small to produce a certain amount of energy,.

2. The nuclear fuel supplies energy over a long span of time.


  1. No source of energy is completely pollution free - only the degree and the manner of pollution varies. A solar cell is pollution free in actual operation but its assembly causes damage to environment.


  1. Hydrogen is a cleaner fuel than CNG. Because it produces water on burning whereas CNG on burning produces CO2, though it is much less than that is produced when coal or oil is burnt.  A spaceship carries oxygen (in liquid form) along with it to burn hydrogen (in liquid form) as a fuel.


  1. (i) Coal (ii) Petroleum and Natural gas.

These sources were formed over millions of years under special conditions.


  1. The reserves of fossil fuels are limited, i.e., exhaustible whereas solar energy in available in abundance, i.e., is inexhaustible.

Fossils fuels cause pollution on burning whereas solar energy is pollution free.

Fossil fuels can provide energy at any required time whereas solar energy becomes unavailable when the sky is covered with clouds.

Fossil fuel is expensive and solar energy is free.


  1. (i) Bio-mass is a renewable source of energy, if we plant trees in a planned manner which is not the case with hydroelectricity.

(ii) The energy from bio-mass can be obtained by using a chullha or a gobar gas plant whereas hydro-electricity requires construction of dams on rivers.

(iii) Bio-mass provides pollution-free energy only when converted into biogas whereas hydroelectricity is fully pollution-free.


  1. (a) Renewable sources of energy 

(i) They can be replaced as we use them 

(ii) They can be used to produce energy again and again.

Non-renewable sources of energy

1. They cannot be replaced once these are used.

Exhaustible sources of energy

Their supply is limited, e.g., coal, petroleum and natural gas.

Inexhaustible sources of energy

Their supply is unlimited, e.g., solar energy, water energy, wind energy, nuclear energy etc.

Renewable sources of energy are inexhaustible whereas non-renewable sources of energy are exhaustible with some exceptions.

For example, biomass is a renewable source of energy only if we plant trees in a planned manner. On the other hand, geothermal energy and nuclear energy though inexhaustible are non-renewable.


  1. (i) Burning of fossil fuels causes’ air-pollution.

(ii) Construction of dams on rivers to generate hydroelectricity destroys large ecosystems which get submerged under water in the dams. A further, large amount of methane, which is a greenhouse gas, is produced when submerged vegetation rots under anaerobic conditions.

Measures to be taken to reduce energy consumption :

(i) Fossil fuels should be used with care and caution to derive maximum benefit out of them.

(ii) Fuel saving devices  should be used for example solar cookers, pressure cookers..

(iii) Efficiency of energy sources should be maintained by regular servicing.

(iv) We should be economical in our energy consumption as energy saved is energy produced.


  1. A source of energy is a system in which output is more than the input. The difference between output and input is the useful energy given by the source.