Lakhmir Singh Class 10 Physics 3rd Chapter Sources of Energy Solution

Lakhmir Singh Manjit Kaur Physics Solution: Sources of Energy Chapter 3. Here you get easy Solutions of Lakhmir Singh Class 10 Physics Solution Chapter 3. Here we have given Chapter 3 all Solution of Class 10. Its help you to complete your homework.

Board – CBSE
Text Book – Physics
Class – 10
Chapter – 03

Lakhmir Singh Class 10 Physics 3rd Chapter Solution

Sources of Energy

Very Short Answer Type Questions :-

1) Name a non-renewable source of energy other than fossil fuels.

Ans:

The non renewable source of energy other than fossil fuels are nuclear fuels like uranium

2) Define calorific value of a fuel.

Ans:

The amount of heat produced by burning a unit mass of a fuel completely is known as it’s calorific value.

3) “The calorific value of cooking gas (LPG) is 50 kJ/g”. What does it mean?

Ans:

The calorific value of cooking gas LPG is 50KJ/g means if 1gram of LPG gas is burnt completely then it will produce 50 kilojoules of heat energy.

4) Which of the following produces more heat (per unit mass) on burning? Coal or LPG

Ans:

LPG produces more heat per unit mass on burning.

5) Define ignition temperature of a fuel.

Ans:

Ignition temperature is the temperature at which a fuel must be heated and due to which it may catch the fire also and hence start burning.
And each and every fuel burns only when we gives it heat to its ignition temperature.

6) The ignition temperature of a fuel is 80°C”. What does this mean?

Ans:

The ignition temperature of a fuel is 80°C means that it is the minimum temperature of the fuel at which it starts heating and after that immediately catch the fire and starts burning.

7) Fill in the following blank with a suitable word:

Ans:-

The amount of heat produced by burning a unit mass of a fuel completely is known as it’s calorific value.

Short Answer Type Questions –

8) What is a source of energy? What are the two main categories of the sources of energy?

Ans:

Sources of energy are those which can provide adequate amount of energy in sufficient form over the long duration of time.
And all the energy sources are divided into two main categories namely non-renewable sources of energy and renewable sources of energy on the basis of their existence and availability.

9) State any four characteristics of a good source of energy.

Ans:

The good source of energy is one which has following characteristics:

That fuel must have to do large amount of work per unit mass.
That fuel must be cheap and have to easily available.
That must be easy to store and also to transport.
That fuel must be safe to handle and use
And main thing is that, it does not produces any kind of pollution.

10) What is meant by a non-renewable source of energy? Give two examples of non-renewable sources of energy.

Ans:

Non-renewable sources of energy are those sources which are produced after long duration of time and after continuous use of this sources may exhaust this type of energy sources and we can’t replace them after they get exhausted.
The non-renewable sources of energy are also called as conventional sources of energy.

For example:

Fossil fuels like coal, petroleum and natural gas, nuclear fuels like uranium are the non-refundable sources of energy as they required long period of time to form and one day they will exhaust.

11) What is meant by a renewable source of energy? Give two examples of renewable sources of energy.

Ans:

Renewable sources of energy are those energy sources which can be produced when we need and their continuous use may not exhaust them, such type of sources are called as renewable energy sources.
Renewable sources of energy are also called as non-conventional sources of energy.

For example:

Wood is the best example of renewable source of energy because we can use wood for producing energy and again we can plant trees to get again energy from wood. Hence wood is the renewable source of energy.
Hydro energy, wind energy, solar energy, geothermal energy, biomass energy all are the renewable sources of energy.

12) What is the difference between a renewable and a non-renewable source of energy? Explain with examples.

Ans:

Non- Renewable sources of energy:

Non- Renewable sources of energy takes long time for their formation.
After continuous use of non-renewable sources of energy they may exhaust one day.
Non-renewable sources of energy are also called as conventional sources of energy.
For example: fossil fuels like coal, petroleum, natural gas, nuclear fuels like uranium are the non-renewable sources of energy.

Renewable sources of energy:

Renewable sources of energy takes very short period of time for their formation.
After continuous use of renewable energy sources they does not exhaust, we can again produce them.
Renewable sources of energy are also called as non-conventional sources of energy.
For example: hydro energy, wind energy, solar energy, energy from sea, geothermal energy, biomass energy are all the renewable sources of energy.

13) Why are fossil fuels classified as non-renewable sources of energy?

Ans:

Fossil fuels are classified as non-renewable energy sources because they are produced over decades.
And after continuous use of fossil fuels like coal, petroleum and natural gas may cause to exhaust them.
After exhaustion they cannot be replaced by any other energy sources quickly.
Because of all the above reasons fossil fuels are classified as non-renewable energy sources.

14) Name two sources of energy that you think are renewable. Give reason for your choice.

Ans:

Solar energy and wind energy are the renewable sources of energy.
Because, sun is the huge source of energy and solar energy coming from the sun is cheap and available anywhere in huge amount.
Also after its use daily does not exhaust it. It is available to each and every person on the earth in same amount.
Similarly, wind energy is also the renewable source of energy because it is available in free of cost.
Also after continuous use of wind energy it does not exhaust and we can use it anywhere and anytime.
Only plant producing electricity from wind energy requires space and costly to some extent.

15) Name two sources of energy which you consider to be non-renewable. Give reason for your choice.

Ans:

Fossil fuels like coal, petroleum are the non-renewable sources of energy because they take long time to form.
Also, after continuous use of this energy sources they get exhausted because they are present in limited.
And we cannot replace them by other energy sources quickly.
Also, nuclear fuels like uranium are present in earth crust in limited form and after their continuous use they may get exhausted.

16) (a) Classify the following into renewable and non-renewable sources of energy: Coal, Wind, Tides, Petroleum, Wood, Natural gas (b) What is the basis of above classification?

Ans:

Renewable sources of energy:

Wind, tides, wood etc.

Non-renewable sources of energy:

Coal, petroleum, natural gas.

The sources of energy are classified into renewable and non-renewable sources of energy on the basis of time period of their formation and their existence after continuous use of them.

17) Coal is said to be formed from the wood of trees. Why then is coal considered to be a non-renewable source of energy whereas wood is a renewable source of energy?

Ans:

Coal is said to be formed from wood of trees but it takes decades to form due to which it is considered as non-renewable source of energy.
And we can plant large number of trees and we may get wood from them during short time period so that wood is considered as the renewable source of energy.

Long Answer Type Question

18)

(a) What is a fuel? Give five examples of fuels.

(b) What are the characteristics of an ideal fuel (or good fuel)?

(c) The calorific value and ignition temperature of fuel A are 55 kJ/g and 80°C, respectively. These values for fuel B are 80 kJ/g and 10°C, respectively. On burning, the fuel A produces CO2 and H2O while the fuel B produces CO2, CO and SO2.

Give three points of relative advantages and disadvantages of these two fuels.

Ans:

Fuels are those materials which on burning produces heat energy.
For example: wood, coal, cooking gas, kerosene, petrol and diesel all are the fuels as they produces heat energy on burning.

Following are the characteristics of an ideal or good fuel:

It should have a high calorific value i.e. it must produces more heat per unit mass.
It should have to burn without producing any harmful gases or smoke i.e. it does not produces any type of air pollution.
It must possess a proper ignition temperature i.e. it must possess neither too low ignition temperature nor too high ignition temperature.
It must be cheap and easily available i.e. it is available in low cost and availability is everywhere.

Fuel A:

Fuel A has low calorific value of 55kJ/g which is the disadvantage.
But fuel A has moderate ignition temperature near about 80°C which is the advantage.
And after burning of fuel A it produces CO2 and H2O which are not harmful. This is also the advantage.

Fuel B:

The fuel B has high calorific value near about 80kJ/g which is the advantage.
It has very low ignition temperature near about 10°C which is disadvantage.
It produces harmful gases like CO2 and SO2 after burning. This is the disadvantage.

Conventional Sources of Energy

Very Short Answer Type Questions

1) Name the product of petroleum that is used to drive heavy vehicles.

Ans:

Diesel is the product of petroleum which is used to drive heavy vehicles.

2) Give one example of a good domestic fuel.

Ans:

LPG i.e. Liquefied Petroleum Gas is the good domestic fuel.

3) Name any one hydrocarbon fraction obtained during the fractional distillation of petroleum which is used as a domestic fuel.

Ans:

Kerosene is one of the hydrocarbon fraction obtained during the fractional distillation of petroleum which is used as domestic fuel.

4) What are the various fuels which are used to generate electricity in a thermal power plant?

Ans:

The various fuels which are used to generate electricity in a thermal power plant are coal, oil or gas.

5) Name any four fractions obtained from petroleum which are used as fuels.

Ans:

The fractional distillation of petroleum gives us the following fractions which can be used as fuels:
Petroleum gas, petrol or gasoline, diesel, kerosene and fuel oil etc.

6) What is the composition of liquefied petroleum gas (LPG)?

Ans:

The liquefied petroleum gas contains mainly butane along with smaller amount of propane and ethane which has been liquefied by applying pressure.

7) Which gaseous fuel is being used increasingly in transport vehicles like cars and buses these days?

Ans:

CNG i.e. Compressed natural gas is being used increasingly in transport vehicles like cars and buses these days.

8) Write the full form of: (i) LPG, and (ii) CNG.

Ans:

The full form of LPG is Liquefied Petroleum Gas
The full form of CNG is Compressed natural gas.

9) What is the main constituent of: (i) petroleum gas? (ii) natural gas?

Ans:

The main constituent of petroleum is butane.
And main constituent of natural gas is methane.

10) Name the component which is found in natural gas as well as in biogas.

Ans:

The component which is found in natural gas as well as biogas is the methane.

11) State two important uses of natural gas.

Ans:

Following are the important uses of natural gas:

Natural gas is used as fuel directly for heating purposes in homes and industries.
It is used as a domestic and industrial fuel.
It is also used as fuel in thermal power plants to generate electricity.
CNG is being used increasingly as fuel in transport vehicles mostly.

12) State one important use of CNG these days.

Ans:

Compressed natural gas i.e. CNG is being used increasingly as fuel mostly in transport vehicles these days.

13) Complete the following sentence:

Ans:

Domestic gas cylinders like Insane contains mainly butane.

Short Answer Type Questions :-

14) Explain why, natural gas is considered to be a good fuel.

Ans:

Natural gas is considered as a good fuel because of the following advantages:
Natural gas is a complete fuel and can be used directly for heating purposes in homes and industries. And no need to add other thing to it.
It also has high calorific value near about 50kJ/g. And it does not produces any smoke after burning and hence there is no air pollution.
Most important thing is that after burning of natural gas it does not produces any poisoning gases hence it is eco-friendly fuel as compared to the other fossil fuels.
Main advantage of natural gas is that it can be supplied directly from gas wells to the homes and factories for burning purpose through underground pipelines also. And we can’t require any additional storage or transport for its supply.
Because of the above all advantages natural gas is considered to be a good fuel.

15) What is meant by conventional sources of energy? Write the names of two conventional sources of energy.

Ans:

Non-renewable sources of energy are those sources which are produced after long duration of time and after continuous use of this sources may exhaust this type of energy sources and we can’t replace them after they get exhausted.
The non-renewable sources of energy are also called as conventional sources of energy.

For example:

Fossil fuels like coal, petroleum and natural gas, nuclear fuels like uranium are the non-refundable sources of energy as they required long period of time to form and one day they will exhaust.

16) Explain the principle of working of a thermal power plant. Draw a labelled diagram to illustrate your answer.

Ans:

A power plant in which heat is produced by burning the fuels like coal, oil or gas to produce the steam to rotate turbines and thereby to generate electricity is called as thermal power plant.

Principle of working of a thermal power plant:

The following diagram shows the principle of working of thermal power plant.
In thermal power plant coal it fuel oil or natural gas is used to produce heat in a furnace F as shown in figure. And after that the heat produced is used to boil the water in boiler B and produces steam.
Due the steam formed in boiler a pressure is developed and this high pressure hot steams are inserted into the turbine chamber C which has steam turbines T.
Due to the high pressure of steam, it passed over the blades of turbine and results in rotating the turbine.
The shaft S is connected to a generator G of turbine. When turbines start rotating the shaft S also rotates and hence drives the generator. And finally generator produces electricity.
And the steam get cooled after coming out of turbine. After cooling the steam it get condensed to form water. And this water is again sent to boiler to from again the fresh steam and complete process is repeated further and further.

17) What are the disadvantages of burning fossil fuels?

Ans:

The burning of fossil fuels has lot of disadvantages which are explained as below:

The burning of fossil fuels may produces such as sulphur dioxide and nitrogen oxides which results to acid rain also.
Also burning of fossil fuels generates large amount of carbon dioxide gas which goes into atmospheric and increases the greenhouse effect.
The burning fossil fuels mainly coal produces smoke which goes into air and produces air pollution.
Also, after burning the coal there is ash will be left behind which may also causes air pollution.

18) Write a short note on the pollution caused by burning fossil fuels.

Ans:

The burning of fossil fuels produces carbon dioxide in large amount which goes into air. As it is not harmful immediately but after long period it causes to increase the greenhouse effect and due to which temperature of the earth will get increased. And which most harmful to all life present on the earth.
Also after burning of fossil fuels smoke is released in the air which also causes the air pollution.
Also, after burning of fossil fuels ash is left behind which goes into air and also causes air pollution.

19) What are the various steps which can be taken to control (or reduce) pollution caused by burning fossil fuels?

Ans:

Following are the steps which can be taken to control or to reduce pollution caused by the burning of fossil fuels:

The air pollution caused due to the burning of fossil fuels like petrol and diesel in vehicles can be reduced by fitting the vehicles with catalytic converters.
Also, the burning of fuel in thermal power plants and factories causing air pollution can be reduced by washing down the smoke and also the acidic gases by water in a scrubber.
The pollution produced due to burning of coal in thermal power plant and factories can be controlled by installing the electrostatic precipitation in their chimneys.

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

Ans:

We use LPG for heating food because it has high calorific value hence it is a good fuel. And the calorific value of LPG is near about 50kJ/g.
Which means when 1g of LPG is burnt out then it produces 50kJ of heat energy.
Also after burning of LPG no smoke will be produced and hence no air pollution.
Also after burning of LPG there will be no poisonous gases will be produced.
Main thing is that LPG is easy to handle and also to store.
And it is the very neat and clean domestic fuel.

21) Why is LPG considered a good fuel?

Ans:

LPG is considered as a good fuel because of the following reasons:

We use LPG for heating food because it has high calorific value hence it is a good fuel. And the calorific value of LPG is near about 50kJ/g.
Which means when 1g of LPG is burnt out then it produces 50kJ of heat energy.
Also after burning of LPG no smoke will be produced and hence no air pollution.
Also after burning of LPG there will be no poisonous gases will be produced.
Main thing is that LPG is easy to handle and also to store.
And it is the very neat and clean domestic fuel.

22) Why is LPG considered a better fuel than coal?

Ans:

Because after burning of coal there will be smoke is produced which goes into air and causes air pollution.
Also after burning of coal ash will be left behind which also causes air pollution.
Burning of coal produces carbon dioxide in large amount which goes into atmosphere and lead to greenhouse effect.
But, LPG does not produces any air pollution, it is easy to handle and store.
And LPG has high calorific value.
Because of the above all advantages of LPG, it is the better fuel than call.

23) Why is the leakage of LPG detected easily although it is odourless? State the steps to be taken in case its leakage is detected in the kitchen.

Ans:

Before lightning the matchstick in kitchen we should have to check the foul smell of leakage of gas near the gas cylinder or stove.
If there is smell like leakage of gas then we have to open the windows and doors at once and allow to escape the gas through them.
Because LPG is not a poisonous gas but if it is inhaled in large amount then then it is very harmful and may cause death also.
For this we have to check the gas leakage through gas cylinder, rubber tubing and gas stove. And we have use it only when the leakage has been set right by the gas mechanic.
And most important thing is that, we don’t have to light candle or matchstick during the leakage of gas.
For this we have to check rubber pipes connecting the gas cylinder to gas stove periodically. When are not using gas cylinder valve of the gas cylinder and the knobs of the gas stove should be kept closed.

Long Answer Type Question

24) (a) What are fossil fuels? Give three examples of fossil fuels.

(b) Describe how fossil fuels were formed.

(c) Explain how, sun is considered to be the ultimate source of fossil fuels.

(d) Which fossil fuels were formed by the buried remains of small plants and animals?

(e) Which fossil fuel was formed by the buried remains of large land plants?

Ans:

Fossil fuels are the natural fuels formed deep under the earth and pre-historic remains of the living organisms like plants and animals.

For example: coal, petroleum, natural gas are the fossil fuels.

The fossil fuels are formed by the following way:

After death of animals and plants million years ago the were get buried deep in the earth gradually and get covered with some sediments like mud and sand and they were get away from the oxygen of air.
And hence due to the absence of oxygen, the chemical effects of pressure, heat and bacteria converts this buried remains of plants and animals into the fossil fuels like coal, petroleum and natural gas.
In this process the buried remains of large plants get converted into coal while the remains of buried small plants and animals were converted into petroleum and natural gas.
In this way fossil fuels are formed after million of years.

Non-Conventional Sources of Energy:

Very Short Answer Type Questions

1) A hydro-power plant converts one form of energy into another. Name the two forms of energy.

Ans:

A hydro power plant converts potential energy of stored water into electrical energy.

2) What type of energy is possessed by flowing water?

Ans:

The kinetic energy is possessed by the flowing water.

3) Flowing water can rotate a turbine. Which type of energy is used up by the turbine?

Ans:

Flowing water can rotate a turbine that means kinetic energy is used up by the turbine.

4) Name the original source of wind energy.

Ans:

Sun is the original source of energy.

5) What should be the minimum wind speed for the satisfactory working of a wind-powered electric generator?

Ans:

The minimum wind speed for the satisfactory working of a wind-powered electric generator is 15km/hr.

6) Write one use of wind energy (a) in the past (b) at present.

Ans:

In past, the wind energy is used in flour mills.

In present, the wind energy is used to generate electricity in wind-powered electric generator.

7) Why is the copper tube of a solar water heater painted black from outside?

Ans:

The copper tube of a solar water heater is painted black from outside because black colour is good absorbent and hence it absorbs most of the solar energy and hence more heat will be generated in solar water heater to heat the water easily.

8) What type of reactions occurring inside the sun produce solar energy?

Ans:

Nuclear fusion type reactions are occurring inside the sun to produce solar energy.

9) Name some of the solar energy devices.

Ans:

Following are the some solar energy devices:

Solar cooker, solar water heater, solar cells,

10) What type of reflector is used in a box-type solar cooker?

Ans:

A plane mirror type of reflector is used in a box type solar cooker.

11) What is the range of temperature which can be achieved in a box-type solar cooker in two to three hours?

Ans:

The temperature range which can be achieved in a box type solar cooker in two to three hours will be 100°C to 140°C.

12) Name the device which converts sunlight into electricity.

Ans:

Solar cell I the device which converts solar energy into electricity.

13) How much solar energy will be received by 1 m2 area in one hour if the solar constant be 1.4 kW/m2?

Ans:

Area = 1m2

1 hour= 60*60= 3600 seconds

Solar constant = 1.4kW/m2 = 1.4 kJ/s/m2

Thus, energy received in 1 hour will be,

Energy received= 1.4*3600= 5040kJ/m2.

14) Fill in the following blanks with suitable words:

Ans:

A solar cell converts sunlight energy into electrical energy.

Short Answer Type Questions

15) (a) What is the difference between a thermal power plant and a hydro power plant?

(b) Which of the two causes serious air pollution and how?

Ans:

In thermal power plant thermal energy is produced by burning of fuels like coal, petroleum or natural gas.
Whereas in hydro power plants, the flowing water is used to rotate turbines and thereby produces electricity.

In thermal power plants, harmful gases and fly-ash is released in the air which causes the air pollution. Also burning of fossil fuels like coal, petroleum and natural gas may produces carbon dioxide which is released in the air and hence leads to greenhouse effect.

16) Compare the sun and the fossil fuels as the sources of energy.

Ans:

Solar energy is the renewable source of energy which is available in free of cost and everyday.
Also does not produces any kind of pollution and after continuous use it cannot be exhausted.
But, coal is the fossil fuels which is the non-renewable source of energy. And it can be exhausted one day. It takes long time for its production.
And main thing, burning of coal produces CO2 in air which causes air pollution also.

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

Ans:

Concave mirror and also plane mirrors are used in the solar cooker. Because concave mirror converges most of the sunlight incident on it at a particular point where large amount of heat will be generated.
Also plane mirror are fixed at the top of solar cooker due to which most of the sunlight get reflected so that it can be heated more and because of this food will be cooked easily and early.

18) (a) Name that part of a box-type solar cooker which allows the sun’s heat rays to enter the box but does not allow inside heat to go out.

(b) Explain why, a plane mirror reflector is used in a box-type solar cooker.

Ans:

Glass sheet cover is part of a box type solar cooker which allows the sun’s heat rays to enter the box but does not allow inside heat to go out.

In box type solar cooker, plane mirrors are used because it reflects most of the sunlight incident on it and hence strong beam of sunlight will be absorbed which again produces more heat.
And hence helps in cooking food more early and easily.

19) What are the advantages and disadvantages of using a solar cooker?

Ans:

The advantages of solar cooker are as follows:

If we are using solar cooker for cooking food that means it saves most of the fuels like coal, petroleum, LPG.
As solar cooker uses solar energy to cook food hence there are no harmful gases are produced causing air pollution.
As food is cooked in solar cooker at lower temperatures, hence the nutrients from the food not get destroyed while cooking.
Mostly we can cook 3-4 foods at a time in solar cooker which is the most important advantage of solar cooker.

The disadvantages of solar cooker are as follows:

As solar cooker is wholly based on the solar energy hence if there is no sunlight we cannot cook food or in night time we cannot cook food.
Although if the day-sky is covered with clouds then also sufficient solar energy is not available to cook food.
We have to change the direction of face of solar cooker so that it can receive solar energy directly.
And box type solar cooker cannot be used for making chapattis or for drying.

20)

(a) What is a solar cell? Draw the labelled diagram of a solar cell.

(b) Name the semi-conductor material which is usually used for making solar cells.

(c) Write the uses of solar cells.

Ans:

Solar cell is the device which uses solar energy to produce electricity.
The following diagram shows the solar cell.

Silicon is the semiconductor material which is usually used for making solar cells. Also solar cell consist of sandwich of a silicon-boron layer and a silicon-arsenic layer.

Following are the uses of solar cells:

The electricity produced by solar cell can be used in artificial satellites and space probes.
The electricity produced by solar cell can be provided to remote, inaccessible and isolated places where normal electricity transmission lines do not exist.
Also, solar cells are used to transmit radio and television programs in remote areas.
Also electricity produced by solar cell can be provided to light houses situated in the sea and to off shore oil drilling rig platforms.
Mostly solar cells are used for operating traffic signals, watches, calculators and toys also.

21) State the advantages and disadvantages of using solar cells.

Ans:

Following are the advantages of solar cell:

The solar cells not have any moving part, they did not require may maintenance, and work satisfactorily without using any light focusing device.
Another advantage is that they can be in remote, inaccessible and very sparsely inhabited areas where the electricity transmission is difficult and expensive.

Following are the disadvantages of solar cell:

To make solar cell special silicon grade is required which is very expensive.
While making solar cell panel, silver wire is used to interconnect the solar cells which is also most expensive.
In short, to make solar cell we need expensive materials and hence it is the not convenient.
Also solar cell has low efficiency to generate electricity.

22) What is a solar cell panel? For what purpose is it used? State its two main advantages.

Ans:

A solar cell panel is the device which consist of large number of solar cells which are joined together in definite pattern.
Large number of solar cell are interconnected using silver wires and forms the solar panels which produces large amount of electrical energy. Since silver is the best conductor of electricity.
The advantages of solar panel is that it can be constructed in those places where usually electricity is not available.

23) (a) What is solar constant? What is the value of solar constant?

(b) If the energy received by 5 m2 area in 10 minutes is 4200 kJ, calculate the value of solar constant.

Ans:

Solar constant is nothing but the amount of solar energy received per second by the one square meter area near the earth space at an average distance between the sun and the earth.

The value of solar constant is 1.4kJ/s/m2 or 1.4kW/m2.

Given that,

Area= 5m2

Time = 10 min= 10*60= 600 seconds

Energy= 4200 kJ

We know that,

Solar constant = energy/(time*area)

= 4200/(600*5) = 4200/ 3000

Solar constant= 1.4KJ/s/m2 = 1.4KW/m2

24) How has the traditional use of energy of flowing water been modified for our convenience?

Ans:

Many years ago when there were no industrialization, water flow was used for many purposes which are not efficient. That time flow of water is used to make flour from wheat and also to transport the materials like wood. But this methods was not efficient.
Now a days, we are using running water to generate electricity on large scale. And which is the best use of water flowing with high kinetic energy.

25) How has the traditional use of wind energy been modified for our convenience?

Ans:

Many year ago, the wind energy was used to lift or draw the water from wells which was not efficient method. But now a days, the wind with high speed is used to rotate turbines and to generate electricity.
Also, big dams are constructed to generate electricity. And waterfalls are also used to generate electricity.
So now a days we are using best methods to generate electricity without causing any kind of pollution.

Long Answer Type Questions

26) (a) What is hydroelectricity? Explain the basic principle of generation of hydroelectricity with the help of a labelled diagram.

(b) State two advantages of producing hydroelectricity.

(c) State two disadvantages of producing hydroelectricity.

Ans:

Hydro electricity is the technique by which flowing water can be used to generate electricity.
Hydro power plants are uses flowing water to rotate turbines and thereby produces electricity.
The following diagram shows the principle of working of hydro power plant.
Rain falling on the high hills will be moved to the rivers. So to produce electricity high rise dams D is builder to stop the flowing river water. Due to which a large lake or dam will be developed behind the dam. As more water is collected the water level of dam rises to greater heights.
In this way, the kinetic energy of flowing water is converted into the potential energy of stored water in the dam. This water stored behind the dam has large amount of potential energy.
The sliding gates having height half of the dams are opened to allow some water to escape from the reservoir. And this water is taken to Piper P and provided to the turbine T which are installed at the bottom of the dams.
As water is falling down from large height it’s potential energy get converted into kinetic energy and which is used to rotate the turbines rapidly. These turbines are connected to generator through shaft S. In this way, when turbines get rotated shaft so starts rotating and hence drives the generator. So that generator produces electricity.

Following are the advantages of producing hydro electricity:

The generation of electricity from flowing water does not causes any type of pollution.
And flowing water is the renewable source of energy to generate electricity and hence it can never be exhausted.
Also construction of dams on rivers helps in controlling floods and in irrigation also.

Following are the disadvantages of producing hydro electricity:

To construct dams large area of land, a vast variety of flora and fauna as well as human settlements get submerged in the water of reservoir formed due to dams. Due to which many plants get destroyed and animals get killed and most of the people lost their homes.
Also large ecosystem get destroyed when land is submerged into the water to construct big dams.
Due to the construction of dams on the river the fishes which are at the downstream do not get nutrients and hence fish production will be deceased.

27)

(a) With the help of a labelled diagram, explain the construction and working of a solar cooker.

(b) Why is the solar cooker box painted black from inside?

(c) Why is the solar cooker box covered with a glass sheet?

Ans:

Solar cooker is used to cook the food by producing heat energy from the solar energy which is absorbed.

Construction of solar cooker:

The following diagram shows the box type solar cooker.
It consist of an insulated metal box or wooden box which is painted black from inside totally. And there is thick glass sheet cover over the box and plane mirror reflector is also connected to the box as shown in figure.
The food which we have to cook is will be placed inside the chamber which is painted black from inside totally.
These metals containers are then placed inside the solar cooker box and they are covered with glass sheet also.

Working of solar cooker:

To cook food solar cooker are placed in sunshine outside our house. Reflector is made such that it totally faces to the sun and when Sundays get reflected from the reflector they are sent to the top box of solar cooker in the form of string beam of sunlight.
These sun rays get incident on the glass sheet and get absorbed by the black paint so that they are not get reflected back again.
Due to the absorption of more and more sun rays there will large heat is produced which increases the ten of the solar cooker upto 100°C to 140°C in 2-3 hours.
And hence the food kept in black container will be cooked fastly.
In box type solar cooker, only food like rice, pulses and vegetables can be cooked.

Solar cooker box is painted black from inside because when strong beam of sunlight is incident on it then it get totally absorbed and not reflected back again.
Due to which large amount of heat is generated in the solar cooker box which is required for cooking food.

Solar cooker is covered with glass sheet because when strong beam of sunlight is incident on it , it get absorbed without causing any reflection further.
So heat will be produced more and food get cooked easily.

28)

(a) What is wind? What type of energy is possessed by wind?

(b) Explain how, wind energy can be used to generate electricity. Illustrate your answer with the help of a labelled diagram.

(c) State two advantages of using wind energy for generating electricity.

(d) Mention two limitations of wind energy for generating electricity.

Ans:

The moving air is called as wind. The wind possess kinetic energy.

Wind generator are used to generate electricity from wind energy.
The following diagram shows the neat labelled diagram of wind generator.
When the fast moving wind is strikes the blades of the wind turbine, then blades start rotating continuously. And shaft of wind turbine is connected to small generator which produces electricity.
The electricity produced in a single turbine is very small and hence large number of turbines are erected over a big area of land.
Such large number of turbines working at a place on large land to produce electricity from wind are called as wind energy farms. In this way, small electricity produced will be combined together to form the electricity on large scale.

Following are the advantages of using wind energy for generating electricity:

The most important advantage of using wind energy to produce electricity is that it does not produces any kind of pollution.
Also, wind energy is the renewable source of energy which cannot be exhausted.
As long as sun is glowing, wind is flowing and we can generate electricity.
By producing electricity using wind energy may conserve the fossil fuels and reduce pollution also.

Following are the limitations of using wind energy for generating electricity:

Wind energy farms cannot be established everywhere because they can be established only in those areas where wind is blowing for most part of the year.
The minimum speed of wind required for generating electricity is 15km/h which is not always possible.
To construct wind energy farms large area of land is required.
And to construct and set up the wind energy farms is too expensive.

Biomass Energy

Very Short Answer Type Questions

1) What substance is obtained as a residue when wood is burned in a limited supply of air?

Ans:

Charcoal is obtained as a residue when wood is burned in a limited supply of air.

2) Name one source of energy which is not derived from solar energy directly or indirectly.

Ans:

Geothermal energy is one of the source of energy which is not derived from solar energy directly or indirectly.

3) What name is given to the heat energy obtained from hot rocks inside the earth?

Ans:

The heat energy obtained from hot rocks inside the earth is named as geothermal energy.

4) Name the agent which decomposes animal dung into biogas.

Ans:

Anaerobic bacteria is the agent which decomposes animal dung into biogas.

5) Which component of biogas is used as a fuel?

Ans:

Methane is the component of biogas which is used as a fuel.

6) Name the constituents of biogas.

Ans:

The constituents of the biogas are methane, carbon dioxide, hydrogen and hydrogen sulphide.

7) Which of the following is needed for the formation of biogas from cow-dung and which not? Water, Oxygen

Ans:

Water is needed for the formation of biogas from cow dung while oxygen is not required for the formation of biogas from cow dung.

8) Name the clean fuel which can be obtained from cow-dung.

Ans:

Biogas is the clean fuel which can be obtained from cow dung.

9) Apart from cattle dung, what other substances can be added to a biogas plant?

Ans:

Apart from cattle dung, plant wastes are also added to a biogas plant.

10) Name any three forms of energy which could be harnessed from the sea.

Ans:

Following are the forms of energy which could be harnessed from the sea:

Tidal energy
Wave energy
Ocean thermal energy

11) Write two forms in which solar energy manifests itself in sea.

Ans:

Sea wave energy and ocean thermal energy are the two forms in which solar energy manifests itself in sea.

12) Write the full form of OTE.

Ans:

The full form of OTE is Ocean Thermal Energy.

13) What is the function of anaerobic micro-organisms such as anaerobic bacteria in a biogas plant?

Ans:

The animal wastes like cow dung or plant wastes are degraded anaerobically in biogas plant by using anaerobic microorganisms such as anaerobic bacteria.

14) State whether the following statement is true or false: Tidal energy is one of the forms in which solar energy manifests itself in oceans.

Ans:

The above statement is false because sea wave energy and ocean thermal energy are the two forms in which solar energy manifests itself in ocean.

15) Fill in the following blanks with suitable words:

Ans:

A) Biomass is another form in which solar energy manifests itself.

B) Tidal waves build up and recede twice a day.

Short Answer Type Questions

16) (a) What is biomass? Give three examples of biomass.

(b) Name the biomass which is still widely used as a source of heat energy in many households of our country.

Ans:

The plant waste like trees, dead plants and animal wastes like cow dung is the biomass. Biomass is the organic matter which is used to produce energy.

For example: the plant wastes, wood, animal wastes like cow dung, agricultural waste all are the examples of biomass.

Wood and cow dung cakes are the examples of biomass which are still used as a source of heat energy in many households of our country.

17) What are the two ways in which cow-dung can be used as a fuel? Which of them is better and why?

Ans:

Cow dung can be used in two ways to produce energy.
One way is the direct using cow dung cakes to produce energy for cooking food.
And second one is the cow dung is used in biogas which produces no smoke.
As biogas does not produces any kind of pollution in air it is better fuel as compared to cow dung cakes. And the cow dung remained after processing in biogas can be also used as manure as it contains all nutrients needed for plant growth.

18) How is charcoal prepared? Explain why, charcoal is a better fuel than wood.

Ans:

When wood is burnt in limited supply of air then water and also all the volatile materials present in it get removed and black substance is remained left which is called as charcoal.

Charcoal is better fuel than wood because of the following reasons:

Charcoal has high calorific value than wood due to which charcoal produces more heat than the equal mass of wood.
Charcoal does not produce any kind of pollution while burning where as wood produces lot of smoke and hence causes air pollution.
Also, charcoal is the compact fuel which is easy to handle and most convenient to use than wood.

19) Compare and contrast biomass and hydroelectricity as sources of energy.

Ans:

Biomass is the renewable source of energy and hydroelectricity is also the renewable source of energy.
After burning the biomass may cause air pollution but hydroelectricity does not causes any type of pollution.
The energy produced by biomass can be used only for cooking purpose and heating. But hydroelectricity can be used to run all types of electrical appliances.
In biomass we cannot need any special device to obtain energy but in hydroelectricity we need to establish hydro power plant.

20) Why is biogas considered an ideal fuel for domestic use?

Ans:

Biogas is considered as an ideal fuel for domestic use because of the following reasons:

Biogas after burning does not produces smoke and hence no air pollution.
It has high calorific value due to which it produces large amount of heat energy per unit mass.
Biogas is the clean fuel as it does not left any residue after burning.
No storage will be needed for biogas as it is directly supplied through pipes from gas plant.
Main thing is that it is the cheapest fuel among all the fuels.

21) (a) Explain how tidal energy can be used to generate electricity.

(b) Why is tidal energy not likely to be a potential source of energy?

Ans:

Due the gravitational pull of the moon there is change in water level of sea. When there is rise in water level of sea it is called as high tide and when there is fall in water level of sea it is called as low tide.
These tidal waves build up and rise and falls twice a day. The movement of water between the high tide and low tide provides large source of energy and this tidal energy can be harnessed by constructing a tidal barrage or tidal dam across narrow opening at the sea.

The tidal energy is not likely to be a potential source of energy in future because of the following reasons:

All over world there are very few sites where tidal dams are constructed.
The rise and fall in water level of sea is not sufficient to produce electricity on large scale.

22) State the two ways in which the energy of sea waves can be harnessed?

Ans:

Following are the two ways in which energy of sea waves can be harnessed:

In one case floating generators are developed on sea which moves with sea waves up and down. This up and down movement drives the generator in order to produce electricity.
In another method, sea waves are set to move up and down inside large tubes. When waves move up the air will be compressed in the tube which is then used to rotate turbines of generator and electricity will be produced.

23) What is meant by ocean thermal energy? Explain how ocean thermal energy can be used to generate electricity.

Ans:

The energy which is available due the temperature difference of water at the surface of ocean at the deeper level is called as ocean thermal energy.
The device which is used to produce ocean thermal energy is called as ocean thermal energy conversion power plant. To operate OTEC it needs 20°C temperature between the water on surface and deeper water.
In one type of OTEC power plant, warm water surface of ocean is used to boil liquid like ammonia or CFC. And the high-pressure vapours formed of boiling liquid are used to rotate turbines of a generator and electricity is produced.
The cold water from the deeper of ocean is used to cool the water vapours and then get converted into liquid. Thus, the process is repeated again and again. And electricity will be produced on large scale.

24) What are the limitations of energy that can be harnessed from the sea?

Ans:

Following are the limitations of energy that can be harnessed from the sea:

All over world there are very few sites where tidal dams are constructed.
The rise and fall in water level of sea is not sufficient to produce electricity on large scale.

25) Suggest a safe and efficient method for the disposal of bio wastes and sewage materials. How is this method advantageous to us?

Ans:

The safe and efficient method for the disposal of bio wastes and sewage materials is to use them in biogas which produces energy and also manure without producing any kind of pollution.
Also, after burning biomass no smoke is produced and hence no pollution.

26) Which of the following sources of energy are not derived from the sun? Biomass, Wind, Ocean thermal energy, Geothermal energy, nuclear fuels, Hydroelectricity, Wave energy, Coal, Petroleum, Tidal energy

Ans:

The sources of energy which are not derived from the sun are geothermal energy, nuclear energy, hydroelectricity, energy obtained from coal and petroleum.

Long Answer Type Questions

27)

(a) What is biogas? Name the major component of biogas.

(b) What are the raw materials used for making biogas?

(c) Describe the construction and working of a biogas plant with the help of a labelled diagram. (d) Write any two uses of biogas.

(e) Write any two advantages of using biogas.

Ans:

Biogas is the mixture of gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.
The major component of biogas is methane.

The raw materials used for making biogas are cow dung, animal and plant waste, agricultural wastes etc.

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 is 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.

Fig. Schematic diagram of Biomass

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 biogases 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.

Following are the uses of biogas:

Biogas is used as good fuel for cooking.
It is also used for lighting.
It is also used to run engines.
It is also used to generate electricity

Advantages of using biogas:

Biomass is the renewable source of energy.
It can be used without using any special device for producing energy.
It is used to run engines and also to generate electricity.

28) (a) What is geothermal energy?

(b) What is the source of heat contained in geothermal energy?

(c) Explain how, geothermal energy is used to generate electricity.

(d) State two advantages of geothermal energy.

(e) State two disadvantages of geothermal energy.

Ans:

Geothermal energy is the heat energy o rained from hot rocks present inside the earth.

Hot spots where very hot rocks occur at some depth below the surface of earth are the sources of heat contained in geothermal energy.

The hot rocks present below the earth surface or which are underground heats the water due to which steam is generated. As more steam is formed between rocks and hence it gets compressed to high pressure.
Where such rocks are present the hole is drilled and pipes are put into it. And that seams around the rocks is taken up through pipes at high pressure.
This high-pressure steam rotates the turbines of generator and hence electrify is produced.

Following a re the advantages of using geothermal energy:

It is economical to use geothermal energy.
The use of geothermal energy does not cause any kind of pollution.

Following are the disadvantages of using geothermal energy:

Geothermal energy is not available everywhere. It is available only in those area where hot rocks are present under earth crust
To obtain geothermal energy we have to deep drill in the earth which is very difficult and expensive.

Nuclear Energy

Very Short Answer Type Questions

1) What type of nuclear reaction is responsible for the liberation of energy:

(a) in a nuclear reactor?

(b) in the sun?

Ans:

In nuclear reactor nuclear fission type of reaction is responsible for the liberation of energy.

In the sun nuclear fusion type of reaction is responsible for the liberation of energy.

2) Which product of the nuclear fission of uranium-235 is utilised to cause further fission of its nuclei ?

Ans:

Neutrons are the product of the nuclear fission of uranium-235 is utilised to cause further fission of its nuclei.

3) Which particles bring about the fission of uranium-235?

Ans:

The slow moving neutrons brings about the fission of uranium-235.

4) State whether the fission of uranium-235 is caused by low energy neutrons or high energy neutrons.

Ans:

The fission of uranium -235 is caused by low energy neutrons.

5) Name the type of nuclear reaction which is involved in the working of:

(a) a hydrogen bombs.

(b) an atom bombs.

Ans:

In the working of hydrogen bomb the nuclear fusion type of reaction is involved.

In the working of atom bombs nuclear fission type of nuclear reaction is involved.

6) Name the moderator used in a nuclear reactor.

Ans:

Graphite is the moderator used in a nuclear reactor.

9) Where, in a nuclear power station, is uranium used up?

Ans:

In nuclear power stations, in reactors uranium is used up.

10) State one use of nuclear fission reactions.

Ans:

The highly destructive nuclear bomb or atom bomb is mainly based on the nuclear fission reaction of uranium-235 or plutonium-239.

11) Name the unit which is commonly used for expressing the energy released in nuclear reactions.

Ans:

The energy released in nuclear reactions is expressed in electron volt (eV) or Million electron volt (MeV).

12) How many MeV are equivalent to 1 atomic mass unit (u)?

Ans:

1 atomic mass (u) = 931 MeV

13) Fill in the following blanks with suitable words:

Ans:

Splitting of a heavy nucleus into two lighter nuclei is called nuclear fission.
Uranium-235 atoms will split when hit by neutrons. This is called nuclear fission.
Nuclear fission is used in nuclear power stations for the production of electricity.
In a nuclear power station, nuclear fission takes place in the reactor.

Short Answer Type Questions :-

14) What is nuclear fission? Explain with an example. Write the equation of the nuclear reaction involved.

Ans:

The nuclear reaction in which heavy radioactive nuclei like uranium, plutonium or thorium get spilted into smaller nuclei when they get bombarded with low energy neutrons is called as nuclear fission reaction.

For example:

When uranium-235 atoms are bombarded with slow moving neutrons, the heavy uranium is solutes into barium-139 and kryoton-94 along with the emission of 3 neutrons.
Also, large amount of energy is produced during this nuclear fission reaction which is expressed in equation form as follows:

15) (a) What is nuclear fusion? Explain with an example. Write the equation of the reaction involved.

(b) Why are very high temperatures required for fusion to occur?

Ans:

The nuclear reaction in which two lighter nuclei get combined to form the heavy nucleus is called as nuclear fusion reaction.

For example:

When we heat deuterium atoms to an extremely high temperature and under high pressure then two deuterium atoms get combined and forms the heavy nucleus of helium with the release of a neutron and large amount of energy.

The following is chemical equation showing nuclear fusion reaction.

We know that, in nuclear fusion reaction two lighter nuclei get combined to form a heavy nucleus. And as nuclei of atoms are positively charged due to which when two positive nuclei get brought together they repels each other.
Because of this we require large amount of heat energy and high pressure initially to force the lighter nuclei fuse together and to form the heavy nucleus.
Hence, nuclear fusion reaction needs million of degree of temperature and million of Pascal of pressure.

16) What is the nuclear fuel in the sun? Describe the process by which energy is released in the sun. Write the equation of the nuclear reaction involved.

Ans:

The hydrogen gas is the nuclear fuel in the sun.

We receives heat and light energy front he sun from many years which is due to the fusion of hydrogen nuclei into helium nuclei which goes inside it and hence large amount of heat will be produced.

On the sun, four hydrogen atom nuclei get fused to form the bigger nucleus of helium atom which is expressed in the form of equation as below.

17) (a) Write Einstein’s mass-energy equation. Give the meaning of each symbol which occurs in it.

(b) If 25 atomic mass units (u) of a radioactive material are destroyed in a nuclear reaction, how much energy is released in MeV?

Ans:

According to Einstein the mass and energy are equivalent and it gave the relationship between mass and energy which is called as Einstein’s mass energy relation.
It is given by, E= mc²
Where, E is the amount of energy generated when mass m get destroyed
And c is the speed of light in vacuum.

We know that,

1 atomic mass unit= 931 MeV

Hence, 25 atomic mass unit = 25*931= 23275 MeV

18) (a) What is the source of energy of the sun and other stars?

(b) Describe the working of a hydrogen bomb.

(c) What is common between the sun and a hydrogen bomb?

Ans:

On the sun and stars, nuclear fusion reaction takes place at high temperatures and pressures in which lighter hydrogen nuclei get fused together to form the heavy helium nuclei with the release of tremendous amount of energy.

Nuclear reactions occuring at very high temperature are used to produce weapons of mass destruction which are called as hydrogen bomb.
It consists of heavy isotopes of hydrogen named as deuterium and tritium and also lithium. And hydrogen bomb explosion takes place using atom bomb.
When atom bomb get exploded then due to fission reaction large amount of heat is produced which raises the temperature of deuterium and tritium to 10⁷°C in few microseconds.
At such a high temperature the fusion reaction of deuterium and tritium takes place to produce tremendous amount of energy.
Due to which hydrogen bomb explosion takes place with the release of tremendous amount of energy in a very short time. This energy is the reason for causing destruction of life and property.
The lithium-6 in hydrogen bomb is used to form more tritium which are needed for fusion reaction. Thus, we can say they hydrogen bomb is based in the thermonuclear fusion reactions of heavy hydrogen atoms like deuterium and tritium in order to produce helium atoms.

In the sun as well as in the hydrogen bomb energy is produced by nuclear fusion reactions.

19) (a) What will happen if slow moving neutrons are made to strike the atoms of a heavy element 235 92U? What is the name of this process?

(b) Write a nuclear equation to represent the process which takes place.

(c) Name one installation where such a process is utilised.

Ans:

The nuclear reaction in which heavy radioactive nuclei like uranium, plutonium or thorium get spilted into smaller nuclei when they get bombarded with low energy neutrons is called as nuclear fission reaction.
Here, the nuclear reaction takes place is called as nuclear fission reaction.

When uranium-235 atoms are bombarded with slow moving neutrons, the heavy uranium is solutes into barium-139 and kryoton-94 along with the emission of 3 neutrons.
Also, large amount of energy is produced during this nuclear fission reaction which is expressed in equation form as follows:

In the nuclear power stations such a process is utilised.

20) (a) What are the advantages of nuclear energy?

(b) State the disadvantages of nuclear energy.

Ans:

Following are the advantages of nuclear energy:

It produces the tremendous amount of energy which is useful from the small amount of nuclear fuel.
In nuclear reactors, once the nuclear fuel get loaded then nuclear power plant works to produce electricity for two to three years at a stretch. There no need to put nuclear fuel again.
It does not produces CO2 causing greenhouse effect and also not produces sulphur dioxide causing acid rain.

Following are the disadvantages of nuclear energy:

The waste products if nuclear fission reactions are very radioactive which may emits nuclear radiation a for many years. Hence, it is very difficult to dispose and store nuclear ease materials.
There will be most possibility of accident in nuclear reactor due to leakage of nuclear radioactive materials which may cause damage or harms to plants, animal and to the environment also.
Nuclear power plants requires lot of cost to install and there is also limited availability of nuclear fuels which is the disadvantage of nuclear power plant producing energy.

21) The following questions are about the nuclear reactor of a power plant.

(a) Which isotope of uranium produces the energy in the fuel rods?

(b) Will the fuel rods last for ever?

(c) Is the energy produced by nuclear fission or nuclear fusion?

(d) What is the purpose of using the graphite moderator?

(e) What is the function of boron rods in the nuclear reactor?

(f) Why is liquid sodium (or carbon dioxide gas) pumped through the reactor?

Ans:

Uranium-235 is the isotope of uranium which produces the energy in the fuel rods.

The fuel rods would not last for ever.

The energy produced will be by nuclear fission reaction.

In nuclear power plants, graphite is used as moderator which slows down the speed of neutrons to make them fit for causing fission

Boron rods are called as control rods because they absorbs the excess neutrons and thereby prevent the fission reaction going out of control.

The liquid sodium or carbon dioxide gas is used as coolant to transfer the heat produced in the reactor by fission to heat boiler to convert water into steam.

22) In the reactor of a nuclear power plant, name the material which is used:

(a) as a moderator

(b) to absorb radiations

(c) in the fuel rods

(d) in the control rods

(e) to carry away heat

Ans:

In nuclear power plant, graphite is used as moderator.

To absorb the radiation’s the reactor is enclosed in a concert chamber.

Uranium-235 is used in the fuel rods.

Boron rods are used as control rods.

Liquid sodium or carbon dioxide gas is used to carry away heat.

23) In the nuclear reactor of a power plant:

(a) how do control rods control the rate of fission?

(b) how is heat removed from the reactor core, and what use is made of this heat?

Ans:

In between uranium rods boron rods are inserted which are called as control rods. They control the rate of fission by absorbing excess neutrons.

In nuclear reactors, liquid sodium or carbon dioxide gas is used as coolant which transfer the heat produced in the reactor by fission to the heat boiler to convert water into steam.

24) How does inserting the control rods in the graphite core affect the fission in the reactor? Explain your answer.

Ans:

Uranium -235 rods are inserted in the core of graphite block, where graphite rods are called as moderator. Graphite rods slows down the speed of neutrons to make so that they cause fission.
In between uranium rods boron rods are inserted which are called as control rods as they absorb excess neutrons and prevent the nuclear fission which goes out of control.

25) What are the advantages and disadvantages of using nuclear fuel for generating electricity?

Ans:

Advantages of using nuclear fuel for generating electricity:

In nuclear power plant, nuclear fuel is used to produce electricity which is required in less amount than the fossils fuels used to generate same amount of electricity.
In nuclear power plant, there is no emission of carbon dioxide gas which not leads to greenhouse effect.
Also, it does not releases sulphur dioxide causing acid rain.

Disadvantages of using nuclear fuel for generating electricity:

To build nuclear power plant the cost required is too large. So it is expensive method of generating electricity.
Due to the release of hot water from nuclear power plant, it causes thermal pollution.
Also, there is most possibility of causing accident in nuclear power plants.

Long Answer Type Questions

26) (a) What is a nuclear reactor? What is the fuel used in a nuclear reactor?

(b) With the help of a labelled diagram, describe the working of a nuclear power plant.

(c) How is the working nuclear reactor of a power plant shut down in an emergency?

(d) Name five places in India where nuclear power plants are located.

Ans:

Nuclear reactors are those devices which are constructed to maintain the nuclear chain reaction which produces steady flow of electrons when heavy nuclei get fissioned.
The isotope of uranium which is uranium-235 is used as fuel in a nuclear reactor.

The following diagram shows the neat labelled diagram of nuclear reactor.

The working of nuclear power plant is as given below.

When uranium -235 undergoes controlled nuclear fission reaction then large amount of heat energy is produced.
Liquid sodium or carbon dioxide gas is used to pump continuously through the pipes which are inserted in reactors by using pump P.
The heat produced in reactor is absorbed by sodium. After that the heated sodium is passed over the coil of heat exchanger H which contains water in it.
Where heat is absorbed by the water from hot sodium and boils to form the steam.
The hot steams at high pressure are introduced in to the turbine chamber C where turbines T are present.
Due to the high pressure created turbines get rotated. And shaft S of turbines which is connected to generator G. When turbines rotates due high pressure hot steam the shaft starts to rotate also and hence drives the generator which then produces electricity.

The control rods of boron are fully inserted in the reactor which absorbs all the neutrons which results in shutting down the reactor.

The nuclear power plants are located at:

Tarapur in Maharashtra
Kalpakkam in Tamil Nadu
Narita in Uttar Pradesh
Kaprapur in Gujrat
Kaiga in Karnataka

27(a) Differentiate between nuclear fission and nuclear fusion.

(b) Which of the two, nuclear fission and nuclear fusion, is made use of:

(i) for the production of electricity?

(ii) for making a hydrogen bomb?

(c) Which produces more energy: nuclear fusion or nuclear fission?

(d) Calculate the energy released in joules when 5 g of a material is completely converted into energy during a nuclear reaction.

(e) How much is this energy in MeV? (Speed of light = 3 × 108 m/s)

Ans:

Nuclear fission reaction:

In this nuclear reaction, the heavy radioactive nuclei get splitters into smaller nuclei when low energy neutrons are bombarded on it with the release of tremendous amount of energy.
The energy produced during nuclear fission reaction is used to generate electricity.
In hydrogen bomb explosion nuclear fission reaction takes place.
The energy released is only due to conversion of mass into energy.

Nuclear fusion reaction:

In nuclear fusion reaction two or more lighter nuclei get combined to form the heavy nucleus with the release of tremendous amount of energy.
On the sun, the heat energy produced is only due to nuclear fusion reaction.
In nuclear fusion reaction, the energy produced is not controlled for long time.
The energy released is only due to conversion of mass into energy.

1) to produce electricity nuclear fission reaction is used.

2) to make hydrogen bomb nuclear fusion reaction is used.

The nuclear fusion reaction produces more energy.

Given that,

Mass= 5g = (5/1000) kg

We know that, Einstein’s mass energy relation is given by,

E= m*c2

E= (5/1000)*(3*10⁸)²= 4.5*10¹⁴ J

Thus, the energy released in joules will be 4.5*10¹⁴ J

We know that,1J = 1/1.602*10^-13MeV

Hence, 4.5*10¹⁴ J = 4.5/1.602*10¹⁴*10¹³= 2.8*10²⁷ MeV

Thus, energy released in MeV will be 2.8*10²⁷ MeV.

Environmental Consequences

Very Short Answer Type Questions

1) Which of the two is a cleaner fuel: hydrogen or CNG? Why?

Ans:

Hydrogen is cleaner fuel than CNG because after burning of hydrogen gas only water is produced and which does not causes any kind of pollution.
While after burning of CNG CO2 and water is produced which causes greenhouse effect.

2) Which of the two is more energy efficient: filament type electric bulb or CFL? Why?

Ans:

CFL are conventional filament type bulbs which are more energy efficient because use of more energy efficient electrical appliances save the electricity.

3) How long are the energy resources of the earth like coal, petroleum and natural gas expected to last?

Ans:

The energy resources of the earth like coal are expected to last far another 200 years as compared to 40 years for petroleum oil reserves and also 60 years for saved natural gas.

4) Name two devices which can be utilised for the cooking of food so as to save fuel.

Ans:

Following are the two devices which can be utilised for the cooking of food so as to save fuel:

Solar cooker and pressure cooker etc.

Short Answer Type Questions :-

5) What are the various factors which we should keep in mind while choosing a source of energy?

Ans:

Following are the various factors which we should keep in mind while choosing a source of energy are as follows:

The method of extracting the energy from that source of energy.
We have to check the efficiency of that method which is available to extract the energy from that type of energy sources.
We have to keep in mind what are the dangerous effects of using that type of source for producing energy.

6) Can any source of energy be pollution free? Explain your answer with an example.

Ans:

As we know that, the use of wind generator, solar cooker and solar cells doesn’t cause any kind of pollution when we use them for obtaining energy. But the methods which are used to make such type of devices may harm the environment one day.
So we can say that, no source of energy can be said to be pollution free.

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

Ans:

The following are the environmental consequences of the increasing demand for energy:

We are using fossil fuels on large scale for producing energy but after combustion of fossil fuels harmful gases are releasing in the environment which may cause acid rain, death of plants and animals and also it harms to aquatic life.
As the use of fossil fuels is increased the emission of CO2 in atmosphere is also increased which causes greenhouse effect.
The deforestation for producing energy from wood is also harmful because due to which wild life is exhausting and soil corrosion also may occurs.
The ecological balance get disturbed due to the building of large hydro power plants.
Also, nuclear power plant emits radioactive radiation in the environment which also leads to air pollution and dangerous effects on human health also.

8) What steps would you suggest to reduce energy consumption?

Ans:

The steps that reduces energy consumption are as follows:

We have switch off lights, TV an fans when we don’t have need of them so electricity will be saved.
We have to use energy efficient electric devices like CFL and tube lights to save electricity.
We have to use good quality stoves so that we can produce large amount of energy from burning of kerosene and LPG .
We have to use mostly pressure cookers in kitchen for cooking food.
Sometimes we have to use solar cookers to cook food and we have to use solar water heater to heat the water and to save fuels for future generations.
In rural area we have to create awareness about using of biogas to save fossil fuels.

Here is your solution of Lakhmir Singh Class 10 Physics 3rd Chapter Sources of Energy Solution

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