# NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Written by Team Trustudies
Updated at 2021-05-07

## NCERT solutions for class 10 Science Chapter 14 Sources Of Energy Exercise

Q1 ) A solar water heater cannot be used to get hot water on
(a) a sunny day
(b) a cloudy day
(c) a hot day
(d) a windy day

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(b) a cloudy day, Because solar energy is required for it which is not available on cloudy day.

Q2 ) Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar gas
(c) nuclear energy
(d) coal

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(c) nuclear energy Bio-mass is a source of energy that is obtained from plant materials and animal wastes. Nuclear energy is released during nuclear fission and fusion. In nuclear fission, uranium atom is bombarded with low-energy neutrons. Hence, uranium atom splits into two relatively lighter nuclei. This reaction produces huge amount of energy. In nuclear fusion reaction, lighter nuclei are fused together to form a relatively heavier nuclei. This reaction produces tremendous amount of energy. Hence, nuclear energy is not an example of bio-mass energy source

Q3 ) 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
(c) Nuclear energy
(d) Bio-mass

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(c) Nuclear energy Nuclear energy is released during nuclear fission and fusion. In nuclear fission, uranium atom is bombarded with low-energy neutrons. Hence, uranium atom splits into two relatively lighter nuclei. This reaction produces huge amount of energy. In nuclear fusion reaction, lighter nuclei are fused together to form a relatively heavier nuclei. The energy required to fuse the lighter nuclei is provided by fission reactions. This reaction produces tremendous amount of energy. These reactions can be carried out in the absence or presence of sunlight. There is no effect of sunlight on these reactions. Hence, nuclear energy is not ultimately derived from Sun's energy.

Q4 ) Compare and contrast fossil fuels and the Sun as direct sources of energy.

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Fossil fuels are energy sources, such as coal and petroleum, obtained from underneath the Earth's crust. They are directly available to human beings for use. Hence, fossil fuels are the direct source of energy. These are limited in amount. These are non-renewable sources of energy because these cannot be replenished in nature. Fossil fuels take millions of years for their formation. If the present fossil fuel of the Earth gets exhausted, its formation will take several years. Fossil fuels are also very costly.

On the other hand, solar energy is a renewable and direct source of energy. The Sun has been shining for several years and will do so for the next five billion years. Solar energy is available free of cost to all in unlimited amount. It replenishes in the Sun itself.

Q5 ) Compare and contrast bio-mass and hydro electricity as sources of energy.

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Bio-mass and hydro-electricity both are renewable sources of energy. Bio- mass is derived from dead plants and animal wastes. Hence, it is naturally replenished. It is the result of natural processes. Wood, gobargas, etc. are some of the examples of bio-mass.

Hydro-electricity, on the other hand, is obtained from the potential energy stored in water at a height. Energy from it can be produced again and again. It is harnessed from water and obtained from mechanical processes.

Q6 ) What are the limitations of extracting energy from - (a) the wind? (b) waves? (c) tides?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(a) Wind energy is harnessed by windmills. One of the limitations of extracting energy from wind is that a windmill requires wind of speed more than 15 km/h to generate electricity. Also, a large number of windmills are required, which covers a huge area.

(b) Very strong ocean waves are required in order to extract energy from waves.

(c) Very high tides are required in order to extract energy from tides. Also, the occurrence of tides depends on the relative positions of the Sun, Moon, and the Earth.

Q7 ) 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?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(a) The source of energy that replenishes in nature is known as renewable source of energy. Sun, wind, moving water, bio-mass, etc. are some of the examples of renewable sources of energy.

The source of energy that does not replenish in nature is known as non-renewable source of energy. Coal, petroleum, natural gas, etc. are some of the examples of non-renewable sources of energy.

(b) Exhaustible sources are those sources of energy, which will deplete and exhaust after a few hundred years. Coal, petroleum, etc. are the exhaustible sources of energy.

Inexhaustible resources of energy are those sources, which will not exhaust in future. These are unlimited. Bio-mass is one of the inexhaustible sources of energy.

Q8 ) What are the qualities of an ideal source of energy?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

An ideal source of energy must be:
$?$ Economical
$?$ Easily accessible
$?$ Smoke/pollution free
$?$ Easy to store and transport
$?$ Able to produce huge amount of heat and energy on burning

Q9 ) What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Solar cooker uses Sun's energy to heat and cook food. It is inexhaustible and clean renewable source of energy. It is free for all and available in unlimited amount. Hence, operating a solar cooker is not expensive. Disadvantage of a solar cooker is that it is very expensive. It does not work without sunlight. Hence, on cloudy day, it becomes useless. The places where the days are too short or places with cloud covers round the year, have limited utility for solar cooker.

Q10 ) What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Industrialization increases the demand for energy. Fossil fuels are easily accessible sources of energy that fulfil this demand. The increased use of fossil fuels has a harsh effect on the environment. Too much exploitation of fossil fuels increases the level of green house gas content in the atmosphere, resulting in global warming and a rise in the sea level.

It is not possible to completely reduce the consumption of fossil fuels. However, some measures can be taken such as using electrical appliances wisely and not wasting electricity. Unnecessary usage of water should be avoided. Public transport system with mass transit must be adopted on a large scale. These small steps may help in reducing the consumption of natural resources and conserving them.

It is necessary to look for alternate sources of energy as the present once are getting exhausted at a very fast rate and future generations may face a big problem.

## NCERT solutions for class 10 Science Chapter 14 Sources Of Energy Intext Exercise

Q1 ) What is a good source of energy?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

A good source of energy is one that can be easy to access,easy to transport and store,is economical and does a large amount of work per unit volume or mass.

Q2 ) What is a good fuel ?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

A good fuel is one which has the following properties :

1. It should be fairly cheap and easily available.
2. Its ignition temperature should be above normal temperature.
3. It should be easy to handle and transport.
4. It should not produce any poisonous material during burning and after burning it should not leave any residue or ash behind.
5. Its combustion rate should be steady and controllable.
6. It should have high calorific value so that it produces a high amount of energy for each unit of mass or volume.

Q3 ) If you could use any source of energy for heating your food, which one would you use and why?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

I would use cooking gas like LPG(Liquefied Petroleum Gas) as it fulfills many of the criteria of a good fuel like its good calorific value and non-polluting characteristics etc.

Q4 ) What are the disadvantages of fossil fuels?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

(i) The burning of fossil fuels produces large amounts of air pollutants like carbon dioxide that increases greenhouse effect and also produces acidic gases such as sulphur dioxide and nitrogen oxide which causes acid rain.
(ii) Fossil fuels cannot be replenished in a short time because it takes millions of years to form them.

Q5 ) Why are we looking at alternate sources of energy?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

The demand for energy is rising because of the growing population. Fossil fuels and nuclear fuels may not last long for the coming future and also burning them is causing undesirable effects of pollution. Hence, we need to find an alternate source of energy which is renewable and environment friendly.

Q6 ) How has the traditional use of wind and water energy been modified for convenience ?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Before in the earlier decades,wind and water energy were used for serving several purposes but were not efficient.For e.g. windmills were only used to power smaller mills like flour mills or saw mills and the flow of water was used for transporting wooden logs.But now-a-days windmill farms are constructed to produce electricity and also the traditional use of energy of flowing water has been modified by establishing hydro-power plants which means a better and more efficient use of these forms of energy.

Q7 ) What kind of mirror; concave or convex or plain would be best suited for use in a solar cooker? Why?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

A concave mirror is best suited for use in a solar cooker because the concave mirror converges and focuses the solar energy(sunlight) at a very small area which enables it to create high temperature which is sufficient to cook the food.

Q8 ) What are the limitations of the energy that can be obtained from the oceans?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Limitations of energy which can be obtained from the oceans:

(i)Human habitation in a large portion would get affected because these forms of energy can be harnessed only in the coastal area.

(ii)The technologies for harnessing them are still at an experimental stage and hence are very costly and less efficient.

Q9 ) What is geothermal energy?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Geothermal energy is the energy which can be harnessed from the heat of inside of the earth or in other words,Geothermal energy is thermal energy generated and stored in the Earth.

Q10 ) What are the advantages of nuclear energy?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

The advantages of nuclear energy are as follows :

(i)a large amount of useful energy can be produced from a very small amount of a nuclear fuel .

(ii)a nuclear power plant is more efficient than other power plants because once the nuclear fuel like uranium-235 is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.

(iii)It does not produce harmful gases like carbon dioxide which contributes to greenhouse effect or sulphur dioxide which causes acid rain.

Q11 ) Can any source of energy be pollution free? Why or why not?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

No source of energy can be perfectly pollution free but many sources like biomass energy, hydroelectric energy, wind energy, geothermal energy and solar energy are almost pollution free. If fossil fuel is allowed to burn in presence of excess of oxygen, the pollution produced can be reduced to a good extent.

Q12 ) Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Hydrogen is much cleaner fuel than CNG because while the burning of hydrogen only water is produced, which is totally harmless but on the other hand, burning of CNG produces carbon dioxide gas and water. The carbon dioxide can produce greenhouse effect in the atmosphere in the long run.

Q13 ) Name two energy sources that you would consider to be renewable. Give reasons for your choices.

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy

Solar energy and wind energy are examples of renewable energy sources because they get quickly replenished.

Q14 ) Gives the names of two energy sources that you would consider to be exhaustible. Give reasons for your choice.

NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy