# Lakhmir Singh Solutions Class 10 Physics Chapter 3 Sources Of Energy

There are different sources of energy that are used worldwide for the generation of power. These sources of energy are broadly classified into two types and they are renewable energy and non-renewable energy. There are many countries that are dependent on fossil fuels as their source of energy.

Fossil fuels are non-renewable sources of energy and results in the production of greenhouse gases. Examples of sources of energy include solar energy, wind energy, hydroelectricity, hydroelectric, biomass energy, nuclear energy, and geothermal energy.

Also, renewable sources of energy have its own advantages such as they are sustainable and abundant amount is available in nature. These sources of energy do not contribute to global warming so it can be said that they are eco-friendly in nature.

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Page No: 121

Q1. Name a non-renewable source of energy other than fossil fuels.

Nuclear fuels such as uranium is a non-renewable source of energy other than fossil fuels.

Q2. Define calorific value of a fuel.

Calorific value of a fuel is defined as the amount of heat that is produced by burning completely 1 gram of fuel.

Q3. “The calorific value of cooking gas is 50kJ/g”. What does it mean?

The calorific value of cooking gas is 50kJ/g means that if 1 gram of LPG is completely burnt then the amount of heat energy produced will be equal to 50kJ.

Q4. Which of the following produces more heat per unit mass on burning?

Coal or LPG

Among coal and LPG, LPG will produce more heat per unit mass on burning because it has higher calorific value.

Q5. Define ignition temperature of a fuel.

Ignition temperature of a fuel is defined as the minimum temperature that is required by the fuel in which it gets heated so that it can catch fire and start burning.

Q6. “The ignition temperature of a fuel is 80 degree Celsius”. What does this mean?

The ignition temperature of a fuel is 80 degree Celsius means that the minimum temperature required by the fuel to catch fire before burning is 80 degree Celsius.

Q7. Fill in the blanks with a suitable word:

The amount of heat produced by burning a unit mass of a fuel completely is known as its ………. value.

Calorific value.

Q8. What is a source of energy? What are the two main categories of the sources of energy?

A source of energy is defined as the source from which an adequate amount of energy can be obtained for a long period of time. Following are the two main categories of the sources of energy:

a) Renewable source of energy

b) Non-renewable source of energy

Q9. State any four characteristics of a good source of energy.

A good source of energy will have following four characteristics:

a) Storage and transportation is easy.

b) The energy can be handled with ease and is safe.

c) The energy is easily available.

d) The amount of work done per unit mass is large.

Q10. What is meant by a non-renewable source of energy? Give two examples of non-renewable sources of energy.

A non-renewable source of energy is defined as the source of energy which will exhaust very soon if used for a long period of time. These sources of energy are present in nature in limited amount. Examples of non-renewable sources of energy are coal and petroleum.

Q11. What is meant by a renewable source of energy? Give two examples of renewable sources of energy.

A renewable source of energy is defined as the source of energy which is present in nature in large quantities and can be used for a very long period of time, they never exhaust. Examples of renewable source of energy are solar energy and wind energy.

Q12. What is the difference between a renewable and a non-renewable source of energy? Explain with examples.

The difference between a renewable and a non-renewable source of energy is that renewable source of energy is available in abundant amount in nature whereas non-renewable source of energy is limited. The overuse of none-renewable source of energy will result in exhaustion of them.

Examples of renewable source of energy are solar and wind energy while examples of non-renewable source of energy are coal and petroleum.

Q13. Why are fossil fuels classified as non-renewable source of energy?

Fossil fuels are classified as non-renewable source of energy because once it used it cannot be regained.

Q14. Name two sources of energy that you think are renewable. Give reason for your choice.

Air and water are two sources of energy that are renewable because they are available in large quantities in nature and can be used repetitively.

Q15. Name two sources of energy which you consider to be non-renewable. Give reason for your choice.

Petroleum and coal are the two sources of energy that are non-renewable. This is because once they are used completely, they cannot be regained.

Q16. 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?

a) Renewable sources of energy: wind, tides, and wood

Non-renewable sources of energy: coal, petroleum, and natural gas.

b) The above classification of sources of energy is based on the inexhaustible and exhaustible characteristic of renewable and non-renewable sources of energy respectively.

Q17. 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?

Coal is considered to be a non-renewable source of energy while wood is considered to be a renewable source of energy because the accumulation of coal takes longer period than growing tress. Therefore, using coal at a very high rate will result in exhaustion of coal and therefore, it is considered to non-renewable source of energy.

Q18. 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 55kJ/g and 80 degree Celsius respectively. These values for fuel B are 80kJ/g and 10 degree Celsius 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.

a) Fuel is defined as the substance that is burnt to produce heat energy. Wood, LPG, coal, kerosene, and diesel are the five examples of fuels.

b) Following are the characteristics of fuel:

i) The calorific value must be high.

ii) The ignition temperature of the fuel should be proper.

iii) The fuel should be readily available and inexpensive.

iv) When the fuel is burnt, there should not be release of harmful gases.

c) Fuel A:

i) The calorific value is low that is 55kJ/g which is a disadvantage

ii) The ignition temperature is 80 degree Celsius which moderate and is an advantage

iii) There are no harmful gases produced which is an advantage.

Fuel B:

i) The calorific value is high that is 80kJ/g which is an advantage

ii) The ignition temperature is 10 degree Celsius which is a disadvantage

iii) Harmful gases are released and that is the disadvantage

Multiple Choice Questions

Q19. An example of a renewable source of energy is:

a) petrol

b) natural gas

c) biogas

d) kerosene

The correct answer is c) biogas

Q20. A non-renewable source of energy is:

a) wood

b) alcohol

c) hydrogen gas

d) natural gas

The correct answer is d) natural gas

Q21. Which of the following is not a renewable source of energy?

a) wind

b) flowing water

c) fossil fuels

d) fuel wood

The correct answer is c) fossil fuels

Q22. A good fuel is one which possesses:

a) high calorific value and low ignition temperature

b) high calorific value and high ignition temperature

c) high calorific value and moderate ignition temperature

d) low calorific value and moderate ignition temperature

The correct answer is c) high calorific value and moderate ignition temperature

Q23. The fuel having a calorific value of 55kJ/g is likely to be:

a) biogas

b) methane gas

c) hydrogen gas

d) natural gas

The correct answer is b) methane gas

Q24. A newly planted sapling usually grows and mature into a tree in more than:

a) 50 years

b) 25 years

c) 45 years

d) 15 years

The correct answer is d) 15 years

Q25. Which of the following fuels has the highest calorific value?

a) natural gas

b) methane gas

c) hydrogen gas

d) biogas

The correct answer is c) hydrogen gas

Q26. The fuel having the lowest calorific value is:

a) coal

b) wood

c) charcoal

d) kerosene

The correct answer is b) wood

Q27. There are four fuels which all contain only carbon and hydrogen. The fuel having highest calorific value will be one which has:

a) more of carbon but less of hydrogen

b) less of carbon but more of hydrogen

c) equal proportions of carbon and hydrogen

d) less of carbon as well as less of hydrogen

The correct answer is b) less of carbon but more of hydrogen

Q28. One of the following is not a characteristics of a good fuel. This is:

a) high calorific value

b) no emission of smoke

c) smooth burning

d) high ignition temperature

The correct answer is d) high ignition temperature

Q29. Which of the following is not a fossil fuel?

a) coal

b) petroleum gas

c) biogas

d) natural gas

The correct answer is c) biogas

Page No: 130

Q1. Name the product of petroleum that is used to drive heavy vehicles.

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

Q2. Give one example of a good domestic fuel.

LPG is an example of a good domestic fuel.

Q3. Name any one hydrocarbon fraction obtained during the fractional distillation of petroleum which is used as a domestic fuel.

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

Q4. What are the various fuels which are used to generate electricity in a thermal power plant?

Following are the various fuels that are used in the generation of electricity in a thermal power plant:

Coal, gas, and oil.

Q5. Name any four fractions obtained from petroleum which are used as fuels.

Following are the fraction that are obtained from petroleum that are used as fuels:

Petroleum gas, diesel, kerosene, and petrol.

Q6. What is the composition of liquefied petroleum gas?

The composition of liquefied petroleum gas is butane with smaller amounts of propane and ethane.

Q7. Which gaseous fuel is being used increasingly in transport vehicles like cars and buses these days?

Compressed Natural Gas is used in transport vehicles such as cars and buses.

Q8. Write the full form of: a) LPG b) CNG

a) LPG: Liquefied Petroleum Gas

b) CNG: Compressed Natural Gas

Q9. What is the main constituent of:

a) petroleum gas?

b) natural gas?

a) The main constituent of petroleum gas is butane

b) The main constituent of natural gas is methane

Q10. Name the component which is found in natural gas as well as in biogas.

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

Q11. State two important uses of natural gas.

Following are the two important uses of natural gas:

a) It is used as a fuel in thermal power plants

b) It is used as a fuel in transport vehicles

Q12. State one important use of CNG these days.

One of the important uses of CNG these days is it is used as fuel in transport vehicles.

Q13. Complete the following sentence:

Domestic gas cylinders like Indane contain mainly ……

Butane

Q14. Explain why natural gas is considered to be a good fuel.

Natural gas is considered to be a good fuel because the calorific value of the gas is high and when it is burnt, it burns with smokeless flame resulting in no production of harmful gases.

Q15. What is meant by conventional sources of energy? Write the names of two conventional sources of energy.

Conventional sources of energy is the traditional sources of energy that is familiar to large number of people. Examples of conventional sources of energy are wood and coal.

Q16. Explain the principle of working of a thermal power plant. Draw a labelled diagram to illustrate your answer.

In thermal power plants, heat is produced by burning coal which is used for boiling water to form steam. When the steam with high temperature and pressure is exposed to the turbines, it results in the rotation of turbine and its shaft. This continues rotation of turbine is responsible for the production of electricity.

Q17. What are the disadvantages of burning fossil fuels?

Disadvantages of burning fossil fuels are:

a) Burning of fossil fuels produces acidic gases.

b) The amount of smoke released is more and the amount of ash production is also lot.

c) Greenhouse gases are released during the burning of fossil fuels.

Q18. Write a short note on the pollution caused by burning fossil fuels.

When fossil fuels are burned there is release of acidic gases such as sulphur-dioxide and nitrogen dioxides. These gases are responsible for the acid rains which damages tress, building, and plants, also reducing the fertility of soil. It is also dangerous for the aquatic life. Also, greenhouse gases such as carbon monoxide and carbon dioxide are released. These are the pollution that are caused by the burning of fossil fuels.

Q19. What are the various steps which can be taken to control pollution caused by burning fossil fuels?

Steps that can be taken to control pollution caused by burning of fossil fuels are by increasing the efficiency of combustion process and by finding ways to reduce the release of harmful gases and ashes into nature.

Q20. If you could use any source of energy for heating your food, which one would you use and why?

For heating food, LPG is used as a source of energy because it has a high calorific value and has smokeless flames.

Q21. Why is LPG considered a good fuel?

LPG is considered to be a good fuel because of its calorific value and there is no production of harmful gases. Also, the calorific value of LPG is high.

Q22. Why is LPG considered a better fuel than coal?

LPG is considered to be a better fuel than coal because when coal is burnt harmful gases are released which does not happen when LPG is burnt.

Q23. 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.

LPG is a odourless substance and it is still detected by its odour because of the presence of mercaptan that is added to the LPG.

In case of LPG leakage in the kitchen, following are the steps that must be taken:

a) The doors and windows should be kept open at once so as to allow the gas to escape.

b) Seeking help from gas mechanic is advisable.

Q24. 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?

a) Fossil fuels are the natural fuels that are formed deep under the earth from the pre-historic remains of the organisms. Coal, petroleum, and natural gas are the examples of fossil fuels.

b) Fossil fuels are formed from the dead remains of the animals and plants that died millions of years back. These remains are buried deep inside the earth and are away from the reach of the oxygen. Also, the chemical effects bacteria along with continuous pressure and heat resulted in the formation of fossil fuels.

c) Sun is considered to be the ultimate source of fossil fuel because sunlight is responsible for the growth of plants and animals that are buried inside the earth. Therefore, it can be said that plants and animals are made from sun’s energy and is converted into fossil fuels.

d) Petroleum and natural gas.

e) Coal

Multiple Choice Questions

Q25. The main constituent of petroleum gas is:

a) methane

b) ethane

c) butane

d) propane

The correct answer is c) butane

Q26. The natural gas consists of mainly of:

a) methane

b) ethane

c) propane

d) butane

The correct answer is a) methane

Q27. Which of the following is not produced by the burning of fossil fuels?

a) nitrogen oxides

b) sulphur oxides

c) sodium oxides

d)  carbon oxides

The correct answer is c) sodium oxides

Q28. The product of petroleum used to drive heavy vehicles like trucks is:

a) petrol

b) kerosene

c) petrol

d) CNG

The correct answer is c) petrol

Q29. The aviation fuel which is used in the engines of jet aeroplanes is:

a) diesel

b) kerosene

c) petrol

d) CNG

The correct answer is b) kerosene

Q30. The ultimate source of energy stored in fossil fuels is:

a) moon

b) earth

c) sun

d) sea

The correct answer is c) sun

Q31. Which of the following is not a fossil source of energy?

a) kerosene oil

b) cow-dung cakes

c) CNG

d) coal

The correct answer is b) cow-dung cake

Q32. The fuel which is not used at thermal plants is:

a) coal

b) uranium

c) natural gas

d) fuel oil

The correct answer is b) uranium

Q33. LPG consists mainly of:

a) butane

b) ethane

c) butanone

d) methane

The correct answer is a) butane

Q34. Coke is more valuable when used:

a) as a fuel for industrial boilers

b) as an oxidizing agent

c) as a reducing agent

d) as a fuel in domestic ovens

The correct answer is c) as a reducing agent

Q35. Coal cannot be converted into one of the following forms of energy. This is:

a) coal gas

b) electricity

c) oil

d) charcoal

The correct answer is d) charcoal

Q36. One of the following does not contribute to acid rain. That is:

a) nitrogen monoxide

b) sulphur dioxide

c) carbon monoxide

d) carbon dioxide

The correct answer is c) carbon monoxide

Page No: 140

Multiple Choice Questions

Q29. A solar water heater cannot be used to get hot water on:

a) a sunny day

b) a cloudy day

c) a hot day

d) a windy day

The correct option is b) a cloudy day

Q30. At a hydro power plant:

a) kinetic energy possessed by stored water is converted into electrical energy

b) electricity is extracted from water

c) water is converted into steam to turn turbines and produce electricity

d) potential energy possessed by stored water is converted into electricity

The correct option is d) potential energy possessed by stored water is converted into electricity

Q31. The part of box-type solar cooker which is responsible for producing greenhouse effect is:

a) plane mirror reflector

b) black coating inside the box

c) glass sheet cover

d) utensils placed in the cooker box

The correct option is c) glass sheet cover

Q32. Solar cells are made of:

a) conductors

b) insulators

c) semiconductors

d) superconductors

The correct option is c) semiconductors

Q33. The value of solar constant is:

a) 1.4kWh

b) 1.4kW/m

c) 1.4kW/m2

d) 1.4kW/m3

The correct option is c) 1.4kW/m2

Q34. The radiations present in sunlight which make a solar cooker work are:

a) visible light rays

b) ultraviolet rays

c) cosmic rays

d) infrared rays

The correct option is d) infrared rays

Q35. In order to make an efficient solar cooker, the cover of cooker box should be made of:

a) transparent plastic sheet

b) shining aluminum sheet

c) butter paper sheet

d) transparent glass sheet

The correct option is d) transparent glass sheet

Q36. The minimum speed of wind necessary for the satisfactory working of a wind generator to produce electricity is about:

a) 15km/h

b) 25km/h

c) 35km/h

d) 45km/h

The correct option is a) 15km/h

Q37. If the solar constant is 1.4kW/m2 then the solar energy received by 1m2 area in one hour is:

a) 5040J

b) 504.4kJ

c) 5040kJ

d) 5.04kJ

The correct option is c) 5040kJ

Q38. A solar cooker may not cook food if:

a) the solar cooker is not placed in the shade

b) the glass sheet cover of solar cooker is not closed

c) a convex mirror reflector is not used

d) the food containers of insulating material are not used

The correct option is b) the glass sheet cover of solar cooker is not closed

Page No: 148

Multiple Choice Questions

Q29. Which of the following is not an example of a biomass energy source?

a) wood

b) biogas

c) atomic energy

d) cow-dung

The correct option is c) atomic energy

Q30.most of the sources of energy that we use represent stored solar energy. Which of the following is not ultimately derived from the sun’s energy?

a) wind energy

b) geothermal energy

c) fossil fuels

d) ethane

The correct option is b) geothermal energy

Q31. The constituent of biogas which makes it an excellent fuel is:

a) butane

b) methane

c) propane

d) ethane

The correct option is b) methane

Q32. The major component of biogas is:

a) hydrogen

b) butane

c) hydrogen sulphide

d) methane

The correct option is d) methane

Q33. Which of the following is more environmentally friendly?

a) burning of diesel

b) burning of coal

c) burning of charcoal

d) burning of wood

The correct option is c) burning of charcoal

Q34. Which of the following is not renewable energy technology?

a) solar cells

b) windmills

c) nuclear power

d) tidal power

The correct option is c) nuclear power

Q35. The rise of sea-water during high tide is caused by the gravitational pull of the:

a) sun

b) earth

c) moon

d) mars

The correct option is c) moon

Q36. One of the following is not required in the formation of biogas plant. This is:

a) cow-dung

b) water

c) oxygen

d) anaerobic bacteria

The correct option is c) oxygen

Q37. The fuel which is not obtained from biomass is:

a) firewood

b) cow-dung cakes

c) coke

d) charcoal

The correct option is c) coke

Q38. The non-renewable source of energy among the following is:

a) hydroelectricity

b) sewage gas

c) natural gas

d) gobar gas

The correct option is c) natural gas

Q39. Geothermal energy is produced by the:

b) burning of coal inside the coal mines

c) combustion of natural gas deep inside the earth

The correct option is a) fission of radioactive materials

Q40. The harnessing of which of the following leads to the destruction of large eco-systems?

a) thermal power

b) tidal power

c) hydro power

d) geothermal power

The correct option is c) hydro power

Q41. Which of the following is not a consequence of establishing hydroelectric power plants?

a) displacement of people

b) production of methane

c) occurrence of floods

d) ecological disturbance

The correct option is c) occurrence of floods

Page No: 156

Multiple Choice Questions

Q28. Which of the following is used as a moderator in the reactor of a nuclear power station?

a) liquid sodium

b) boron

c) graphite

d) carbon dioxide

The correct option is c) graphite

Q29. The control rods used in the reactor of a nuclear power plant are made of:

a) steel

b) graphite

c) uranium

d) boron

The correct option is d) boron

Q30. The ‘coolants’ which can be used in the reactor of a nuclear power station are:

a) liquid mercury and nitrogen dioxide

b) liquid sodium and carbon dioxide

c) liquid ammonia and carbon monoxide

d) liquid boron and uranium oxide

The correct option is b) liquid sodium and carbon dioxide

Q31. In a nuclear power plant, coolant is a substance:

a) which cools the hot, spent steam to condense it back to water

b) which transfers heat from reactor to water in heat exchanger

c) which is boiled to make steam to turn the turbine

d) which cools the generator coils to prevent their overheating

The correct option is b) which transfers heat from reactor to water in heat exchanger

Q32. Which of the following is ultimately not derived from the sun’s energy?

a) wind energy

b) nuclear energy

c) biomass energy

d) ocean thermal energy

The correct option is b) nuclear energy

Q33. One atomic mass unit is equivalent to an energy of:

a) 931 eV

b) 9.31 MeV

c) 1 MeV

d) 931 MeV

The correct option is d) 931 MeV

Q34. The energy in the reactor of a nuclear power station is produced by the process of:

a) nuclear diffusion

b) nuclear fission

c) nuclear fusion

d) nuclear fermentation

The correct option is b) nuclear fission

Q35. One eV of nuclear energy is equivalent to:

a) 1.6 × 10-14 J

b) 1.6 × 10-12 J

c) 1.6 × 10-19 J

d) 1.6 × 10-13 J

The correct option is c) 1.6 × 10-19 J

Q36. Which of the following can be produced during the nuclear fission as well as nuclear fusion reactions?

a) protons

b) deuterons

c) electrons

d) neutrons

The correct option is d) neutrons

Q37. Nuclear fission reactions are not a source of energy for one of the following. This is:

a) atom bomb

b) power plants

c) sun

d) pacemaker

The correct option is c) sun

Q38. The energy produced by converting 1 gram mass of a nuclear fuel into energy completely is:

a) 9 × 1016 J

b) 9 × 1014 J

c) 9 × 1015 J

d) 9 × 1013 J

The correct option is d) 9 × 1013 J

Q39. The source of energy of the sun is:

a) conversion of hydrogen gas into helium

b) conversion of carbon fuel into carbon dioxide

c) burning of hydrogen gas present in the sun

d) disintegration of uranium into barium and krypton

The correct answer is a) conversion of hydrogen gas into helium

Q40. An uncontrolled nuclear chain reaction forms the basis of:

a) nuclear power plant

b) hydrogen bomb

c) thermal power station

d) atom bomb

The correct answer is d) atom bomb

Q41. One MeV of nuclear energy is equivalent to:

a) 1.6 × 10-13 J

b) 1.6 × 10-19 J

c) 1.6 × 10-16 J

d) 1.6 × 10-15 J

The correct option is a) 1.6 × 10-13 J

Q42. One type of energy which has not been controlled so far is

a) ocean thermal energy

b) nuclear fusion energy

c) geothermal energy

d) nuclear fission energy

The correct option is b) nuclear fusion energy

Q43. The disposal of wastes produced in a nuclear power plant poses a big problem because it is:

a) too heavy

b) highly inflammable

c) extremely foul smelling

The correct option is d) highly radioactive

Q44. The heat energy released during nuclear fission and fusion is due to the:

a) conversion of stored chemicals into energy

b) conversion of momentum into energy

c) conversion of mass into energy

d) conversion of magnetism into energy

The correct option is c) conversion of mass into energy

Q45. Which of the following can undergo nuclear fusion reaction?

a) uranium

b) deuterium

c) barium

d)  krypton

The correct option is b) deuterium

No: 161

Multiple Choice Questions

Q9. The major cause of environmental pollution is the use of:

a) hydrogen as fuel

b) biomass energy

c) ocean energy

d) fossil fuels

The correct option is d) fossil fuels

Q10. The world’s known coal reserves are expected to last for about:

a) 200 years

b) 400 years

c) 500 years

d) 100 years

The correct option a) 200 years

Q11. The fossil fuel whose known reserves in the earth are expected to last for the minimum period is:

a) coal

b) uranium

c) petroleum

d) natural gas

The correct option c) petroleum

Q12. An energy efficient device for producing light is:

a) DLF

b) CFL

c) FCL

d) LPG