Energy

3. Energy

1 mark question
1. What is energy?
Ans: Energy is defined as the capacity to do work. It is a scalar quantity.
2. What is primary source of energy? Give one example.
Ans: The sources of energy from which we can obtain energy in its natural form i.e without any modification are called primary sources. E.g: solar energy, wind energy etc.
3. What is secondary source of energy? Give one example.
Ans:  The sources of energy from which are used by modification of their natural form are called primary sources. E.g: mineral oil.
4. What is energy crisis?
Ans:The condition of scarcity or shortage of energy due to to over use of non-renewable source of energy for long period of time is called energy crisis.
5. What is alternative source of energy?
Ans: The cheap and durable renewable inexhaustible source of energy used instead of non-renewable source of energy to avoid energy crisis are called the alternative source of energy. Eg. bio-gas, solar energy etc.
6. What is non-renewable energy?
Ans: The source of energy that get depleted and can be used again and again is called renewable energy. Eg. biomass, solar energy, wind energy, tidal energy etc.
7. What is renewable energy?
Ans: The source of energy that does not get depleted and cannot be used again and again is called non-renewable energy
8. What is the advantage of presence of a large amount of hydrogen in the sun?
Ans: The presence of large amount of hydrogen in the sun acts as the fuel to run the thermonuclear fusion reaction under high pressure and temperature.
9. What is the estimated temperature of the outer surface of sun?
Ans: The estimated temperature of the outer surface of sun is about 5700°C.
10. What is nuclear fission?
And: When a heavier nucleus is bombarded with a light projectile which gets split up into lighter nuclei with the release of a large amount of energy is known as Nuclear fission.
11. What is nuclear fusion?
Ans: When two or more light nuclei combine to form a heavy nucleus, there is a tremendous amount of energy is released in the form of heat and light is known as Nuclear fusion.
12. What is hydro power?
Ans: Hydro power or water power is the power obtained from the energy of the falling water or running water which can be used as renewable or alternative source of energy.
13. Define fossil fuel.
Ans: A natural fuel such as coal, gas or petroleum formed from the dead remains of living organism by the geological process is called fossil fuel.
14. What is biomass?
Ans: The domestic waste of garbage which consists of decompose-able organic matter is called the biomass.
15. What is bio-gas?
Ans: The mixture of gases produced by the breakdown of organic matter in the absence of oxygen or limited oxygen is called bio gas.
16. Give any two alternative source of energy.
Ans: The two alternative source of energy are solar energy and bio-gas.
17. State the law of conservation of energy.
Ans: Law of conservation of energy states that energy can neither be created nor be destroyed. It can be transformed into energies of different forms, the total energy before transformation is equal to the sum of different energies obtained after transformation.
18. What is the main element in sun as the source of energy?
Ans: The main element in sun as the source of energy is hydrogen gas.
19. Write some examples of fossil fuels.
Ans: Some examples of fossil fuels are coal. petrol, natural gas etc.
20. What is nuclear energy?
Ans: The energy that is obtained from the nuclear fusion or fission reaction is called nuclear energy.
21. What is nuclear reactor?
Ans: Nuclear reactor is a device used to initiate and control a self-sustained nuclear chain reaction.
22. What is wind energy?
Ans: The energy that is produced by the blowing of air is called wind energy.
23. What is tidal energy?
Ans: A renewable energy powered by the natural rise and fall of oceans tides and currents .
24. What is geothermal energy?
Ans: The heat energy that is produced due to the intern heat of the earth is called geo-thermal energy.
25. Write natural phenomenon from which geothermal energy can be obtained.
Ans: The natural phenomenon from which geothermal energy can be obtained is volcanic eruption and hydrothermal vents.
26. Write down the Einstein's mass energy equation.
Ans: Einstein's mass energy relation is E = mc2
27. Show nuclear reaction that occurs in sun.
Ans: The reaction that occurs in sun is shown below:
${}_{1}{{H}^{1}}+{}_{1}{{H}^{1}}\xrightarrow{\text{High pressure and themprature}}{}_{1}{{H}^{2}}+{}_{1}{{e}^{0}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{1}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{3}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{2}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{3}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+{}_{0}{{n}^{1}}+\gamma (energy)$
${}_{2}H{{e}^{3}}+{}_{2}H{{e}^{3}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+{}_{1}{{H}^{1}}+{}_{1}{{H}^{1}}+\gamma (energy)$
In short,
$_{1}{{H}^{2}}{{+}_{1}}{{H}^{3}}{{\xrightarrow{\text{High pressure and themprature}}}_{2}}H{{e}^{4}}{{+}_{0}}{{n}^{1}}+\gamma (energy)$
Where,
\[_{1}{{H}^{1}}=\text{Protium,}{{\text{ }}_{1}}{{H}^{2}}=\text{Deuterium, }{}_{1}{{H}^{3}}=\text{Tritium,}{{\text{ }}_{1}}{{e}^{0}}=\text{Positorn,}{{\text{ }}_{0}}{{n}^{1}}\text{= neutron }\]
28. Write the fission reaction occurred in splitting of uranium atom.
Ans: The nuclear fission reaction of uranium atom is shown below:
$_{92}{{U}^{235}}{{+}_{0}}{{n}^{1}}{{\xrightarrow{{}}}_{56}}B{{a}^{141}}+{}_{36}K{{r}^{92}}+{{3}_{0}}{{n}^{1}}+\gamma (energy)$
29. List the alternative sources of energy that are relevant to Nepal.

Ans: The alternative sources of energy that are relevant to Nepal are wind energy, solar energy, bio-gas ect.

2 marks questions

31. Write the differences between hydroelectricity and nuclear energy.
Ans: The differences between hydroelectricity and nuclear energy area:

S.no	Hydroelectricity	Nuclear energy
1	It is produced by the flow of water.	It is produced by the splitting or combination of nucleus of atoms.
2	It is eco-friendly source of energy.	It is not eco-friendly source of energy.
3	It produces less energy compared to nuclear energy.	It produces large amount of energy than hydroelectricity.
4	It no harmful byproducts.	It produces harmful byproducts.
5	It can be used for long period of time once it is installed.	Nuclear power plants need to be replaced periodically.

32. Write any two ways to minimize the energy crisis.
Ans: The two ways to minimize the energy crisis are:
i. Development and using Alternative source of energy instead of non renewable source of energy.
ii. Conserving available source of energy and avoiding unnecessary use of fossil fuel.
33. Why should energy be conserved? Mention any two methods that you would take at home          to conserve energy.
Ans: We should conserve energy to make economic use of present energy and to make use and to search for alternative sources of energy as far as possible.
 The two methods that you would take at home to conserve energy are:
i. By utilizing renewable source of energy in place of non-renewable source of energy.
ii. By wise and economic use of energy.
34. "Fossil fuel is also an outcome of solar energy." Justify with reason.
Ans: Fossil fuel is formed from the dead remaining of plants and animals. Pants use solar energy for their growth and development by process of photosynthesis. Animals get their basic needs from plants. When plants animals die, they are buried under the crust. After long period of time under high pressure and temperature turns into fossil fuel. So, fossil fuel is also outcome of solar energy. 
35. What is thermonuclear fusion reaction?
Ans: Thermonuclear fusion reaction is the reaction in which lighter nuclei combined together to form the heavier nuclei in the presence of high temperature and pressure.
36. Natural gas has no smell but on household use we feel bad smell. Why?
Ans:Natural gas is used in many homes for heating, cooking and other home appliances. Natural gas has no smell, which means  is impossible to detect the leakage. That’s why the gas supplier company adds mercaptan, a harmless chemical, to the gas. Mercaptan smells like sulphur, or rotten eggs, to help us identify gas leaks which protects us from potential dangers.
37. Write down any two conditions that is required in sun for nuclear fusion reaction.
Ans: The two conditions that is required in sun for nuclear fusion reaction are:
i. Large amount of fuel i.e hydrogen
ii. Huge pressure and temperature to run thermonuclear fusion reaction.
38. The higher priority has been given for the use of bio-gas energy in Nepal. Give any two
      reasons.
Ans:The higher priority has been given for the use of bio-gas energy in Nepal due to following reasons:
i.  It is cheaper and can be easily be produced
ii. It is environment friendly renewable source of energy.
39. "Nepal has high potentiality of hydro-power electricity." Justify this statement with two               reasons.
Ans: Nepal has high potentiality of hydro-power electricity because of the following reasons:
i. There are more than 6000 rivers that flow fast from high altitudes.
ii. Hydro power stations can produce electricity for long period of time once it is installed.
40. Write any two differences between renewable and non-renewable sources of energy.
Ans:

S.no	Renewable energy sources	Non-renewable energy sources
1	Renewable energy sources can never be used up fully.	These sources of energy can be exhaust (i.e used up or finish) if used up fully.
2	They are renewed by natural cycle.	They are not renewed by natural cycle.

41. In the present world, the use of hydroelectricity is increasing day by day. Write any two              reasons.
Ans: In the present world, the use of hydroelectricity is increasing day by day, the reasons for it are
i. Hydroelectricity is a renewable source of energy .
ii. Hydroelectricity is cheap
42. We might face energy crisis in near future, justify this statement with two regions.
Ans: The population of world is increasing day by day, so as the demand of the energy sources. Most of the present day energy demand is fulfilled by the non-renewable sources of energy like coal, petroleum products, natural gas etc. It takes millions of years to form the non-renewable source of energy but the consumption rate is higher than the production rate which leads to the scarcity of these energy sources which will lead to the energy crisis in near future.
43. Write down two advantages of using geothermal energy.
Ans: Two advantage of using geothermal energy are:-
i. Geothermal energy can be used to generate electricity.
ii. It can be used for booking water in large amount.
44. Write down two advantages of using solar energy.
Ans: Two advantages of using solar energy are:-
i.It is used to generate electricity which can be used as alternative source of energy.
ii. It is clean and green source of energy, so it is environment friendly.
45. Write down difference between nuclear fusion and fission with examples.
Ans: The differences between nuclear fusion and fission reaction are:

S.no	Nuclear fusion	Nuclear fission
1	The nuclear reaction in which lighter nuclei fuse together to form a heavy nucleus with the release of large amount of energy.	The nuclear reaction in which heavier nucleus splits into lighter nucleus with the release of large amount of energy.
2	It releases the more amount of energy than fission reaction.	It releases the less amount of energy than fusion reaction.
3	High temperature and pressure are essential for nuclear fusion reaction.	High temperature and pressure are not necessary for nuclear fission reaction.
4	Hydrogen bomb is made based on fusion reaction.	Atom bomb is made based on nuclear fission reaction.

46. How hydroelectricity is produced?
Ans: The water collected in dam is allow to flow  through the pipe or tunnel that rotates the turbine  about a shaft kept on the axis of rotation of the turbine. The shaft is connected to an electric generator. When the turbine rotates, it also rotates the armature of the generator in a magnetic field and electricity is generated. In this process kinetic energy of flowing water is converted into the electrical energy.
47. Nuclear fuel is non-renewable source of energy but nuclear fission is also considered as alternative source of energy, why?
Ans: Nuclear fuel is non-n renewable source of energy but nuclear fission is also considered as alternative source of energy because it can be used in place of other source of energies as it does not cause global warming by producing greenhouse gases, it is cheap for long term use i.e one the nuclear power station is installed it can be used for long period of time and reduces energy crisis. Nuclear reaction produces relatively more energies than any other source of energy. 
48. Why are coal and mineral fuel called non-renewable source of energy?
Ans: Natural resources like coal, petroleum, and natural gas they takes
thousands of years to form naturally and cannot be replaced as fast
as they are being consumed .
49. Write any two points to justify that ‘Urbanization brings energy crisis’.
Ans: Urbanization brings energy crisis due to the following reasons: 

i. Urbanization increase the demand of energy. 

ii. Over use of non-renewable sources of energy. 
50. Why the use of hydroelectricity is increasing?
Ans: The use of hydroelectricity is increasing because of the following reasons:-
i. Producing hydroelectric power does not pollute environment.
ii. Hydroelectricity energy is renewable and hence it cannot be exhausted .
51. How is geothermal energy utilized?
Ans: Geothermal energy is utilized in the following ways:
i. geothermal energy can be used to generate electricity.
ii.it can be used for boiling water in large amount.
iii.it can be used to heat space in houses and building.
52. Write two differences between bio-gas and liquefied petroleum gas on the basis
of source of energy.
Ans: The two differences between bio-gas and liquefied petroleum gas on the basis of source of energy are: 

S.no	Bio-gas	Liquefied petroleum gas
1	Bio-gas is produced on the surface of the earth.	Liquefied petroleum gas is formed under the crust.
2	It is produced by anaerobic decomposition of animal wastes.	It is produced by the decomposition of dead plants and animals under the rocks due high pressure.

53. Write two difference between renewable and non-renewable energy source of energy.
Ans: The two difference between renewable and non-renewable energy sources are: 

S.no	Renewable energy sources	Non-renewable energy sources
1	Renewable energy sources can never be used up fully.	These sources of energy can be exhaust (i.e used up or finish) if used up fully.
2	They are renewed by natural cycle.	They are not renewed by natural cycle.

54. Why more preference is given for the development alternative sources of energy in the
 today’s world?
Ans: Alternative source of energy replaces the use of non-renewable sources of energy and helps in solving the energy crisis. It also helps in controlling the environment pollution. It is cheap on the long term use i.e it can be used for long period of time once it is installed. Moreover, most of the alternative source of energy is renewable source of energy. 
55. Why fossil fuel is called non-renewable source of energy?
Ans: Fossil fuel is called non-renewable sauce of energy because they are formed from the dead remains of plants and animals that are buried under the surface of the earth's crust for millions of years. These fuels are limited in quantity and can exhaust due to over use by the growing population and takes long period of time to renew it. 
56. Why sun is called the main source of energy?
Ans: Sun is the main source  of heat and light energy on earth. Different types of energy sources in our daily life are the changed forms of solar energy directly or indirectly. Green plants uses sun light to produce food by photosynthesis process. The food produced by plants is consumed by different types of animals to produce energy for their growth and development. Wind blows in the earth's atmosphere due to change in temperature caused by solar energy that helps to run the wind mills and wind turbines. Water cycle maintained by solar energy recharges the under ground water and irrigates the land, runs the electric turbines in hydropower stations. Most of the energy sources that we use today like fossil fuels, bio-fuel, hydroelectricity, tidal energy etc. are dependent upon solar energy directly or indirectly, so, sun is the main source of energy.    
57. Higher priority has been given to the use of bio-gas energy in Nepal. Write any two reasons.
Ans: Higher priority has been given to the use of bio-gas energy in Nepal because of the following reasons: 

i. It is cheapest energy and available very easily. 

ii. It is environment friendly as it does not cause air pollution.

58. Mention any two ways for solving the situation of energy crisis in the context of our country.
Ans: Two ways for solving the situation of energy crisis in the context of our country are: 

1. The renewable source of energy should be used in the place of non-renewable one.

2. Devices based on the solar energy or hydroelectricity should be encouraged 

59. Wind energy is the indirect source of solar energy. Justify it.
Ans: Wind energy is the indirect source of solar energy because the sun unevenly heats different areas of atmosphere due to the earth rotation and differences in surface areas which causes the difference in the air pressure in the atmosphere. Due to the difference in the air pressure air starts to flow from high pressure zones to the low pressure zones. This movement of air produces the wind which can be used as clean and green alternative source of energy. 
60. The use of alternative source of energy helps to control energy crisis, how?
Ans: The use of alternative source of energy helps to control energy crisis because alternative sources of energy are the renewable sources of energy which can replace non-renewable sources of energy like coal, petrol, natural gases, firewood etc. Alternative sources of energies such as nuclear energy, bio-mass energy ,solar energy and many more can be used extensively so that wee can avoid the risk and be able to control energy crisis.
61. What is bio gas? How it is produced?
Ans: Bio gas is the mixture of gases produce by the breakdown of organic matter like cow dung in the absence of oxygen. Bio gas can be produced from raw materials like agricultural waste, cow dung, green waste, food etc. By disintegrating the material inside a closed system.
62. List out four type’s coal.
Ans: The four types of coal are given below.
        i. peat    iv. bituminous     ii.lignite     iii. anthracite
63. Solar energy is regarded as main source of energy why?
Ans: Sun is the main source  of heat and light energy on earth. Different types of energy sources in our daily life are the changed forms of solar energy directly or indirectly. Green plants uses sun light to produce food by photosynthesis process. The food produced by plants is consumed by different types of animals to produce energy for their growth and development. Wind blows in the earth's atmosphere due to change in temperature caused by solar energy that helps to run the wind mills and wind turbines. Water cycle maintained by solar energy recharges the under ground water and irrigates the land, runs the electric turbines in hydropower stations. Most of the energy sources that we use today like fossil fuels, bio-fuel, hydroelectricity, tidal energy etc. are dependent upon solar energy directly or indirectly, so, sun is the main source of energy. 
64. Why are farmers encouraged by government to make bio-gas plant?
Ans: Bio-gas is a kind of bio-fuel obtained from bio-mass i.e. remains or waste products of plants and animals. Most of the people in Nepal depend upon agriculture for economic development. So, bio-gas can easily be obtained from dungs, weeds, waste food etc. It is cheap to install and requires no special skill and knowledge, even a layman can easily install and operate it. Moreover it is clean and green  alternative source of energy. The by products obtained from bio-gas plant can be used as good manure for agricultural products. 
65. Fossil fuels are extensively used nowadays, give two reasons.
Ans: Fossil fuels are extensively used nowadays because of the following reasons: 

i. It is more abundent in comparision to other fuels.

ii. It can generate more power and no alternative has been found to replace it. 

iii. It is cheaper for long term production and can easily be transported from one place to another. 
66. Hydroelectricity is the outcome of solar energy. Justify it.
Ans: Heat energy from sun evaporates the water from sea or oceans which rises up in the sky to form clouds. When the cloud cooled down it returns back to the earth as rain or snow. The rain water flows to the rivers and streams. The speed to water is used to produce hydroelectricity. In this way solar energy maintains the water cycle on the earth. So, hydroelectricity is the outcome of solar energy. 

3 marks questions

67. Write the definition of one calorie heat. Find out the heat and the temperature of the given
      substance with kinetic energy of molecules as shown in figure.

Ans: The amount of heat energy  required to raise the temperature of 1gm of pure water through 1° C is called one calorie heat. One calorie is equal to 4.2 Joule of heat. 

Heat of the given substance  = sum of total K.E of each molecules = 16J

Temperature of the substance = Average K.E of molecules = 16J /5 = 3.2°C

69. Bio-gas is considered as very useful for farmers, why?

Ans: Biogas is the mixture of gases produced by the breakdown of organic matter in the absence of oxygen. Bio gas is considered as very useful for farmers because farmers can produce clean domestic fuel from the wastes like animal dung, dry leaves, dry plants, etc. The byproducts that comes from the bio-gas plants can be used as manure in the fields as manure to increase the fertility of the soil which is environmental friendly also. So biogas is useful for farmers
70. Write down any three applications of the coal and bio-gas.

Ans: Any three applications of bio-gas are:

1. It is used as waste management in the agriculture.

2. It is used as a clean and green renewable fuel for transporting vehicles.

3. It is used in producing electricity.

Three applications of the coal are:

1. It is used in electricity generation.

2. It is used for manufacturing of cement.

3. It is used in different industries like brick factories.

71. Justify with three reasons that the use of hydro-power should be increased than that of coal        and mineral oil for energy.
Ans: Any three reasons that the use of hydro-power should be increased than that of coal and mineral oil for energy are:
i. Hydro power is renewable energy source.
Hydroelectricity uses the energy of running water, without reducing its quantity, to produce electricity. Therefore, all hydroelectric developments, of small or large size, whether run of the river fit the concept of renewable energy.

ii. Hydroelectricity improves the air we breathe.
Hydroelectric power plants don't release pollutants into the air. They frequently substitute the generation from fossil fuels, thus reducing acid rain. In addition to this, hydroelectric developments don't generate toxic by-products.

iii. Hydroelectricity means clean and cheap energy for today and for tomorrow. Once the hydro power plant is installed it can be used to long duration of time. Though it seems costly at first installment it is cheaper for long term use.
so, the use of hydro power should be increased than that of coal and mineral oil for energy.
72. The development and use of alternative energy sources is very necessary
 present world. Explain this statement.

Ans: Alternative source of energy is the clean energy source which do not pollute the environment and it is obtained from nature and renewable source of energy such as biomass, solar, wind, tides, waves, etc.

The development and use of alternative sources is very necessary in present world because these energy sources are not polluting the environment and helping us to reduce the level of greenhouse gas emissions in the atmosphere.using the renewable energy can lower the prices and demand for natural gas and coal by increasing competition and diversifying our energy supplies .

73. Write three conditions required for thermonuclear reaction.

Ans:  Any three condition for thermonuclear reaction are: 

i. Presence of very high temperature i.e about 5700 c

ii. Presence of very high pressure

iii. Presence of large amount of hydrogen gas.

74. What is energy crisis? In the present context, energy crisis may happen soon.
Justify it with two reasons.

Ans: The scarcity of energy in future due to industrialization, urbanization and population growth is called energy crisis. 

In the present context , energy crisis may happen soon. In this present world more energy has been used up due to over population . In the one hand, there has been an over exploitation of the non renewable source of energy and on the other hand there has not been enough search for renewable sources of energy. For example the petroleum products, coal are being finished in their mines the forest are being reduced and the ground water level has decreased. The rate of consumption of the fuel energy is also rapid that they can not last for long time. If the present rate of consumption of fuel energy is continued and no alternative source of energy is are brought into application as a result, the world is likely to face a serious problem of energy crisis.  
75. How is solar energy produced in sun? Explain.

Ans:  Solar energy is created by nuclear fusion reaction which takes place in the sun's core. Fusion occurs when protons of hydrogen atoms violently collide in the sun's core and fuse to create a helium atoms. In each step of the reaction tremendous amount of energy is released. The reaction that occurs in sun is as follow: 

${}_{1}{{H}^{1}}+{}_{1}{{H}^{1}}\xrightarrow{\text{High pressure and themprature}}{}_{1}{{H}^{2}}+{}_{1}{{e}^{0}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{1}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{3}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{2}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+\gamma (energy)$

${}_{1}{{H}^{2}}+{}_{1}{{H}^{3}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+{}_{0}{{n}^{1}}+\gamma (energy)$
${}_{2}H{{e}^{3}}+{}_{2}H{{e}^{3}}\xrightarrow{\text{High pressure and themprature}}{}_{2}H{{e}^{4}}+{}_{1}{{H}^{1}}+{}_{1}{{H}^{1}}+\gamma (energy)$
In short,
$_{1}{{H}^{2}}{{+}_{1}}{{H}^{3}}{{\xrightarrow{\text{High pressure and themprature}}}_{2}}H{{e}^{4}}{{+}_{0}}{{n}^{1}}+\gamma (energy)$
Where,
\[_{1}{{H}^{1}}=\text{Protium,}{{\text{ }}_{1}}{{H}^{2}}=\text{Deuterium, }{}_{1}{{H}^{3}}=\text{Tritium,}{{\text{ }}_{1}}{{e}^{0}}=\text{Positorn,}{{\text{ }}_{0}}{{n}^{1}}\text{= neutron }\]
76. Write three reasons why thermonuclear reaction is not possible on earth.

Ans: The reasons for thermonuclear reaction is not possible on earth are: 

i. There is not plenty of hydrogen on earth.

ii. There is not enough pressrue.

iii. There in not enough temperature to start nuclear fusion reaction 
77. The production and use of hydroelectricity is increasing rapidly in the world.
Write three reason for it.
Ans: 
4 marks questions

78. Hydroelectricity is also an outcome of solar energy. Explain this statement.

Ans:   
79. Justify with any four reasons that the hydroelectricity is the best alternative
source of energy in the context of Nepal.

Ans: The production and use of hydro electricity is increasing rapidly in the world by following reasons:

1.It is a renewable source of energy.

2.It is cheap in the long term.

3.It does not pollute the environment.

80. How can Geo-thermal energy be used? Explain with diagram.

Ans: Geothermal energy can be used in the following ways: 

i. we can use geothermal energy to run steam engine.

ii To generate electricity with the help of geothermal energy can be used.

iii. we can replace gas with geothermal energy because geothermal energy is a source of hot water and we need hot water for kitchen works and many more.  
81. What is mineral oil? How is it mined form the earth surface? Write its two advantages.

Ans:   Ans : Mineral Oil is a formation of decomposition of animals microorganism',plant microscopic , remains buried under the sea or land millions of years ago . And mineral oil is also known as petrol,kerosene and diesel etc. At the present time petrol,kerosene,diesel etc are the source energy .

The process of mining the mineral oil .

IN the oil field oil well is created by drilling a long hole into the earth. A steel pipe is placed in the hole. with the help of pumping machine sucker rod goes up and down and the mineral oil is taken out from the earth surface.

Its advantages are

1 it can be easily transported

2 it is used to run different vehicles and engines

82. All energy are outcome of solar energy. How is solar energy originated? Write with chemical
      reaction.

Ans: Sun is the main source  of heat and light energy on earth. Different types of energy sources in our daily life are the changed forms of solar energy directly or indirectly. Green plants uses sun light to produce food by photosynthesis process. The food produced by plants is consumed by different types of animals to produce energy for their growth and development. Wind blows in the earth's atmosphere due to change in temperature caused by solar energy that helps to run the wind mills and wind turbines. Water cycle maintained by solar energy recharges the under ground water and irrigates the land, runs the electric turbines in hydropower stations. Most of the energy sources that we use today like fossil fuels, bio-fuel, hydroelectricity, tidal energy etc. are dependent upon solar energy directly or indirectly, so, sun is the main source of energy. 

83. Give two reasons behind scientists looking r the development of solar
energy originated? Write with chemical reaction.

 

Numerical