NCERT Exemplar Solution Class 10 Science Chapter 14

NCERT Exemplar Solution Class 10 Science Chapter 14

NCERT Exemplar Solution Class 10 Science Chapter 14 Sources of Energy all Questions Answer Solution. NCERT Exemplar Class 10 Science Chapter 14 Solution PDF.

NCERT Exemplar Solution Class 10 Science Chapter 14: Overview

NCERT Exemplar Solution Class 10 Science Chapter 14

Board

NCERT
Topic

Exemplar Problem Solution

Class

10
Subject

Science

Chapter

14
Chapter Name

Sources of Energy


NCERT Exemplar Solution Class 10 Science Chapter 14 Sources of Energy

Multiple Choice Questions

1.) Which of the following is a non-renewable source of energy?

(a) Wood

(b) Sun

(c) Fossil fuels

(d) Wind

Ans:  (c) Fossil fuels

As fossil fuels are produced after a many years but for the formation of fossil fuels takes too much time. The rate of consuming or using of fossils fuels is greater than its production. Because of this only they are termed as non-renewable source of energy.

2.) Acid rain happens because

(a) Sun leads to heating of upper layer of atmosphere

(b) Burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere

(c) Electrical charges are produced due to friction amongst clouds

(d) Earth atmosphere contains acids

Ans: (b) Burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere

Because due to the burning of fossil fuels and air pollution due to vehicles releases oxides of carbon, nitrogen and sulphur in atmosphere and by mixing with water at a higher height produces acidic pollutants which are responsible for acid rain.

3.) Fuel used in thermal power plants is

(a) Water

(b) Uranium

(c) Biomass

(d) Fossil fuels

Ans: (d) Fossil fuels

The fossil fuel used in thermal power plant is coal which exist in abundant form in the nature and it is cheaper to use and hence it can be used in thermal power plant to produce heat energy.

4.) In a hydro power plant

(a) Potential energy possessed by stored water is converted into electricity

(b) Kinetic energy possessed by stored water is converted into potential energy

(c) Electricity is extracted from water

(d) Water is converted into steam to produce electricity

Ans: (a) Potential energy possessed by stored water is converted into electricity

Because, hydro power plant uses the water which is falling down and it is stored in the dams. This stored water is then used for producing electricity.

5.) Which is the ultimate source of energy?

(a) Water

(b) Sun

(c) Uranium

(d) Fossil fuels

Ans: (b) Sun

Because, sun gives us huge amount of solar energy but whole amount of energy cannot be utilized daily.  Hence, for future it is an ultimate source of energy on the earth.

6.) Which one of the following forms of energy leads to least environmental pollution in the process of its harnessing and utilization?

(a) Nuclear energy

(b) Thermal energy

(c) Solar energy

(d) Geothermal energy

Ans: (c) Solar energy

The solar energy leads to least environmental pollution in the process of its harnessing and utilization. Because, the solar energy coming from sun is free of cost, so it can be used for cooking, heating, producing electricity and in many of the fields. Because, it is more cheaply and not produces any type of pollution in the environment.It is also used in remote areas and in the space also only because of it is not producing any type of pollution.

7.) Ocean thermal energy is due to

(a) Energy stored by waves in the ocean

(b) Temperature difference at different levels in the ocean

(c) Pressure difference at different levels in the ocean

(d) Tides arising out in the ocean

Ans: (b) Temperature difference at different levels in the ocean

Because, there is a huge temperature difference between deep layer of water and the surface water. The deep water is so cool and the water surface is heated due to sunlight and this temperature difference can be used for production of electricity.

8.) The major problem in harnessing nuclear energy is how to

(a) Split nuclei?

(b) Sustain the reaction?

(c) Disposeof spent fuel safely?

(d) Convert nuclear energy into electrical energy?

Ans: (c) Dispose off spent fuel safely?

Because, while harnessing the nuclear energy there is lot of waste materials are produced which are not easily degradable, and it requires proper process to dispose it.

9.) Which part of the solar cooker is responsible for greenhouse effect?

(a) Coating with black color inside the box

(b) Mirror

(c) Glass sheet

(d) Outer cover of the solar cooker

Ans: (c) Glass sheet

Glass sheet is responsible for greenhouse effect in the solar cooker, because it absorbs the infrared radiations from the sunlight to produce heat energy and thereby it used for cooking.

10.) The main constituent of biogas is

(a) Methane

(b) Carbon dioxide

(c) Hydrogen

(d) Hydrogen sulphide

Ans: (a) Methane

Biogas is composed from agricultural waste products like food waste, plant waste which are easily decomposed to produce a mixture of gases in the absence of oxygen. And hence, the main constituent of biogas is methane.

11.) The power generated in a windmill

(a) Is more in rainy season since damp air would mean more air mass hitting the blades

(b) Depends on the height of the tower

(c) Depends on wind velocity

(d) Can be increased by planting tall trees close to the tower

Ans: (c) depends on wind velocity

Because, the wind mills generates electricity on the basis of speed of wind, if the wind is more the blades of the windmill rotates faster to create a huge electricity. And if we observed that, the wind mills are present mostly in those areas where the winds are flowing with high speed.

12.) Choose the correct statement

(a) Sun can be taken as an inexhaustible source of energy

(b) There is infinite storage of fossil fuel inside the earth

(c) Hydro and wind energy plants are non-polluting sources of energy

(d) Waste from a nuclear power plant can be easily disposed off

Ans: (a) Sun can be taken as an inexhaustible source of energy

Because, the energy from the sun is not exhaustible and it is available cheaply without producing any type of pollution. And, the more use of solar energy will decrease the greenhouse effect.

13.) In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because

(a) Its temperature increases

(b) Larger amount of potential energy is converted into kinetic energy

(c) The electricity content of water increases with height

(d) More water molecules dissociate into ions

Ans: (b) Larger amount of potential energy is converted into kinetic energy

Because, in a hydroelectric power plant more electrical power is generated when large amount of potential energy of stored water which is obtained only when the height of falling water is increased which increases the potential energy of water to create more electricity.

14.) Choose the incorrect statement regarding wind power

(a) It is expected to harness wind power to minimum in open space

(b) The potential energy content of wind blowing at high altitudes is the source of wind power

(c) Wind hitting at the blades of a windmill causes them to rotate the rotation thus achieved can be utilized further

(d) One possible method of utilizing the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator

Ans: (b) The potential energy content of wind blowing at high altitudes is the source of wind power

Because, the wind mills produces electricity on the basis of speed of wind flowing only and not on the height of the source of wind power.

15.) Choose the incorrect statement

(a) We are encouraged to plant more trees so as to ensure clean environment and also provide bio-mass fuel

(b) Gobar-gas is produced when crops, vegetable wastes etc., decompose in the absence of oxygen

(c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a lot of residual ash

(d) Bio-mass is a renewable source of energy

Ans: (c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a lot of residual ash

Because, the main ingredient of the biogas is methane which helps in reducing the respiratory diseases.

Short Answer Questions

16.) Why is there a need to harness non-conventional sources of energy? Give two main reasons.

Ans: From the decades, we are using the fossil fuels for the most of the requirements. Sometimes the use of fossil fuel is a unnecessary which creates pollution in environment. Also by burning of fossil fuels like coal, petroleum the harmful gases are entering into the air, which leads to acid rain ozone layer depletion and so on.

If we are increasing the use of fossil fuel again and again then one day it will happen that, the sources of fossil fuels will completely exhausted. In order to decrease the environmental pollution and to save the conventional energy sources for future generation, we have to use it in less amount and only when there will be a real need. And the fossil fuels takes many years to forms.

Hence to save the conventional energy sources and to maintain environmental balance we have to harness non-conventional energy sources also

17.) Write two different ways of harnessing energy from ocean.

Ans: There are two different ways of harnessing energy from ocean.

1) Tidal energy: Tidal energy is harnessed due to the difference in sea levels. The gravitational force of moon on the spinning earth leads to rise and fall in the sea water. The rising and falling of water level is called as high tide and low tide. The dam is constructed near the sea and at its opening a turbine is rotating which converts tidal energy into electrical energy. Tidal energy is the pollution free energy.

2) Wave energy:  Wave energy is also the form of energy harnessed from ocean, which is due to the huge waves in the sea level.  These waves are trapped somewhere and used for producing wave energy. The wave energy is formed due to the strong winds blowing on the sea level which are due to the temperature difference and pressure difference in the atmosphere. In this way from tidal energy and wave energy we can produce electrical energy. The above discussed energies are the two formsof energy harnessed from ocean.

18.) What steps would you suggest to minimize environmental pollution caused by burning of fossil fuels?

Ans: Following are the steps suggested to minimize environmental pollution caused by burning of fossil fuels:

We have to use the vehicles, machines which are working on electricity or energy which cannot produce any type of pollution.

We have to limit the uses of fossil fuels for extra purpose.

The pollutant free energy like wind energy, solar energy and hydropower are the most beneficial forms of energy which we have to use instead of fossil fuels.

We have to ban on deforestation and have to plant more and more trees which will produce pollution free environment in future.

Now a day, lot of factories, vehicles are using fossil fuels in a huge amount and after burning of this fuels there is a evolution of tremendous amount of gases in air which are responsible for air pollution. In order to avoid this we have to use pollutant free energies and have to plant more trees for better environment.

19.) What is the role of a plane mirror and a glass sheet in a solar cooker?

Ans:

Solar cooker is the best alternative for LPG gas. Because, solar cooker uses solar energy to cook the food and it is cheapest method which does not produce any kind of pollution. Mirrors are used in solar cooker to focus the sunlight and thereby increase the temperature to cook food easily and early.

The plane mirrors are used because it reflects all the light incident on it and the glass sheet allows the sunlight to pass through it and get absorbed by cooker inside the box. Because of these the temperature of cooker increases which helps in increasing cooking speed.

Solar cooker is a free form pollution and easy to handle also. Hence, plane mirror and glass sheets are used in solar cookers.

20.) Mention three advantages of a solar cell?

Ans:

The solar cell has vast of advantages because it works on the basis of solar energy which is easily available and does not create any kind of pollution.

The solar cell is a pollution free device and safe to use. Also it has no movable parts, so easy to handle and work. And the solar energy used is in tremendous form which is available to every person on the earth equally and daily.

So we have to only work on it, to produce electricity by using solar cell without giving any harm to environment.

21.) What is biomass? What can be done to obtain bio-energy using biomass?

Ans:

Biogas is the fuel produced from plants and animal waste. The decomposition of cow dung and animal waste, vegetables waste in the absence of oxygen gives biogas.

The main material used is cow dung which is also called as gobar gas. In the biogas plant, the slurry of cow dung and water is placed in a tank to which a sealed chamber is attached where there is no oxygen.

In that chamber anaerobic fermentation of microorganism takes place and after complete decomposition after few days the gases like methane, carbon dioxide, hydrogen, and hydrogensulphide are produced.

Thisgases are stored in the tank above the digester and supplied through the pipe for use. The biogas is most significant and pollutant free to use, because it contains most of the percent of the methane gas and by burning of methane it can’t produce any smoke, ash like wood and not coal also. So it is best for the use and does not harmful to environment also.

And this energy produced is the biomass energy.

22.) What are the limitations in obtaining energy from wind?

Ans:

In case of producing wind energy, we must have large area for wind mills. The speed of wind blowing should be constant but in actual it does not remains constant.

Also, we have to maintain the blades of wind mills properly because they are exposing to all environmental conditions like rain, cyclone and sometime high speed of wind.

Wind energy is produced only in those areas where the speed of blowing wind is high in order to generate electricity in more form. These are the limitations in obtaining electrical energy from wind energy.

Long Answer Questions

23.) Which is the process used to harness nuclear energy these days? Explain it briefly.

Ans:

These days the nuclear power plants, which are using the heat energy produced during nuclear fission reaction mostly. The heat energy evolved during nuclear fission reaction in the core of nuclear reactor is used to boil steam water and which rotates the blades of turbine and helps in producing electricity.

The main reaction is nuclear fission reaction in which a heavy atomic nuclei are bombarded with low energy neutron. In this reaction, fission of reactant nuclei takes place and most of the mass is converted into energy and it is evolved out after reaction.  The difference between mass of reactant nuclei and mass of product nuclei is the amount of energy evolved during the reaction.

The nuclear fission reaction is based on Einstein mass energy relation. The amount of energy evolved which takes main role in generating electricity. But in a nuclear fission reaction, most of the radioactive waste are generated which are more hazardous to the human life and creates water pollution.

The nuclear fission reaction is also used in atom bomb. After explosion of atom bomb huge amount of energy is evolved and radioactive waste are also emitted. There is a dangerous effect of this waste on human health up to thousands of years on human health and generation also.  Thus in this days nuclear fission reaction is used to harness nuclear energy.

24.) How can solar energy be harnessed? Mention any two limitations in using solar energy. How are these limitations overcome?

Ans:

The solar energy is the heat energy in the form of sunlight which is inexhaustible. Each person on the earth receives sunlight equally and free of cost. We have to use only that energy for our daily work and future purpose. The solar energy is the ultimate source of energy for future also. The different ways of using solar energy in daily life are photovoltaic cells which converts light energy into electrical energy, solar panels which are uses sunlight for lightening the bulbs or for working of any electrical devices. Solar cooker which uses sunlight to cook the food also. There are many ways to use solar energy for producing electricity. The limitations in using solar energy are as follows:

Solar energy can be received only in day time and in particular areas mostly. At the time of night we are not receiving solar energy, so to overcome this limitation we have to store the solar energy for the use when it is not available.

The cost of devices, arrangements or appliances which are used in producing electricity from sunlight is very high so everyone cannot afford this arrangement.  To overcome this limitation we have to decrease the cost of the devices or government has to maintain production, demand and cost of that devices by considering everyone’s condition.

 

Solar cell is also called as photo voltaic cell which is used to convert solar energy into electrical energy. It is based on the working of PN junction diode in a semiconductor. On the n-type layer p-type layer is formed and the top surface is coated with anti-reflecting surface to avoid reflection of light and whole light will be absorbed completely. The total surface is coated with protecting glass. When light is incident on the top surface, it get absorbed and potential is developed because of crossing of majority charge carriers. The potential difference developed displaces the charges such as holes to p-side and electrons to n-side and in this way potential difference is developed. If a load resistance is connected current flows through it and electrical energy is produced. In this way solar cell produces electrical energy from solar energy.

25.) Make a list of conventional and non-conventional sources of energy. Give a brief description of harnessing one nonconventional source of energy.

Ans:

  • Conventional energy sources are known as non-renewable energy sources which are having high energy efficiency.
  • But these energy sources are not ecofriendly.
  • If we used them for longer time continuously they will be exhausted.
  • The examples of conventional energy sources are fossil fuels such as coal, oil, wood water, petrol etc.
  • And non-conventional energy sources of energy includes solar power, hydroelectric power, Ocean wave energy, tidal energy, wind energy, solar cell, Ocean thermal power energy, biomass etc. are the non-conventional energy sources.
  • The non-conventional energy sources are ecofriendly and if we use them continuously they will not exhausted.
  • Because they are in exhaustible and they are easy to handle and operate.

Solar cell is also called as photo voltaic cell which is used to convert solar energy into electrical energy. It is based on the working of PN junction diode in a semiconductor. On the n-type layer p-type layer is formed and the top surface is coated with anti-reflecting surface to avoid reflection of light and whole light will be absorbed completely. The total surface is coated with protecting glass. When light is incident on the top surface, it get absorbed and potential is developed because of crossing of majority charge carriers. The potential difference developed displaces the charges such as holes to p-side and electrons to n-side and in this way potential difference is developed. If a load resistance is connected current flows through it and electrical energy is produced. In this way solar cell produces electrical energy from solar energy.

26.) Why is there a need for harnessing non-conventional sources of energy? How can energy be harnessed from the sea in different ways?

Ans:

Conventional energy sources are using day by day rapidly. Because of this use, they will be exhausted early. Therefore we have to make another source which are not inexhaustible and they are only the non-conventional energy sources.

The energy is released from the sea in different ways such as tidal energy, wave energy, thermal energy will be harnessed from the ocean.

1) Tidal energy: Tidal energy is harnessed due to the difference in sea levels. The gravitational force of moon on the spinning earth leads to rise and fall in the sea water. The rising and falling of water level is called as high tide and low tide. The dam is constructed near the sea and at its opening a turbine is rotating which converts tidal energy into electrical energy. Tidal energy is the pollution free energy.

 2) Wave energy:  Wave energy is also the form of energy harnessed from ocean, which is due to the huge waves in the sea level.  These waves are trapped somewhere and used for producing wave energy. The wave energy is formed due to the strong winds blowing on the sea level which are due to the temperature difference and pressure difference in the atmosphere. In this way from tidal energy and wave energy we can produce electrical energy. The above discussed energies are the two forms of energy harnessed from ocean.

3) Ocean thermal energy:  the temperature difference in the upper level and deep level in the sea is used to produce thermal energy called as Austin thermal energy and it is converted into electrical energy.

27.) What are the environmental consequences of using fossil fuels? Suggest the steps to minimize the pollution caused by various sources of energy including non-conventional sources of energy.

Ans:

Because of the extra use of fossil fuels they would be exhausted soon and after burning of fossil fuels, they are producing pollution in environment. The acid rain, global warming, ozone layer depletion are the effects due to the burning of fossil fuels.  Because of the burning of fossil fuels in vehicles mainly the carbon dioxide, nitrous oxide, nitrogen oxides, sulphur oxides and hydrocarbons are produced which are causing to absorb the heat mostly and the temperature of earth’s atmosphere getting increased.

  • Coal mining evolved pyrite and sulphur compound, which are mixed in water and there in mixed with rivers which produces dilute acid after mixing with water. And because of these, the animal and plant life is in danger zone.
  • In the production of electrical energy also most of the extra heat is evolved. This extra heat evolved sometimes ads in air or in water and then it is mixed up with revers and which is again hazardous to animal life living in the water.
  • While in transportation of oil also it is mixed with water of rivers and streams and then it is get polluted.
  • In the mining many times poisonous gases are released which are causing to death of animals. Hence to minimize the pollution caused by various sources of energy we have to do following things:
  • We have to use less fossil fuels and we have to use alternative sources to the fossil fuels like vehicles riding on charging.
  • We have to use the electricity generated by solar cell, wind energy, tidal energy, and wave energy. Also we have to use biomass, solar cooker for cooking the food. The sources which are producing pollution in the environment we have to use them in less amount or we have to use alternative sources to them.
  • In this way we can control the pollution in environment.

28.) Energy from various sources is considered to have been derived from the sun. Do you agree? Justify your answer.

Ans:

Energy from various sources is considered to have been derived from the sun is the correct statement. Because the energy harnessed from any source is the energy derived from the sun directly or indirectly and sun is the ultimate source of energy.

It is a huge and cheapest source of energy.

The wave energy from the sea level is also due to the solar energy and the wave which are generated in sea are having high speed of blowing wind.

The Ocean thermal energy is due to the temperature difference and it is also due to the water heated on the surface level because of solar energy.

The fossil fuels are also produced when plants, animals are buried deep inside the earth’s crust and produces fossil fuels like coal and petroleum in the presence of high heat and pressure.

The solar cooker, solar cell, solar panels are the most used sources of energy which are working only due to the sunlight coming from the sun.

The heavy winds of high-speed are produced due to the temperature and pressure difference in the atmosphere and which is then used to produce electricity.

In plants solar energy is converted into chemical energy by in organic substances and then these plants are also eaten by animals.  The waste products of animal and plants is used in biomass to produce energy.

29.) What is biomass? Explain the principle and working of a biogas plant using a labelled schematic diagram.

Ans:

The biomass uses the animal and plant waste material as a form of fuel. The main source of fuel used is biogas. From decades ago we are using bio mass. The cow dung, plant waste or residue, vegetable waste are decomposed in the absence of oxygen to produce biogas.

The starting material used is only the cow dung.

Principal: The biogas is produced only because of anaerobic fermentation of organic and inorganic waste in the presence of water and absence of oxygen.

Working:

It consists of a dome like structure built with bricks. The slurry of cow dung and water is in the tank where it is supplied to digester. The digester is totally sealed and does not consist of any oxygen.

In the absence of oxygen in the digester anaerobic fermentation takes place and after few days when decomposition is completed the gases such as methane, carbon dioxide, nitrogen and hydrogen sulphide are produced.

These bio gases are stored in the tank above the digester and used through pipe supply.

The biogas that is methane produced is the best fuel because after the burning of methane less amount of smoke is produced in the environment.

Biomass is the eco friendly to use and has no environmental side effects.

Updated: May 14, 2021 — 1:55 am

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