Energy
Energy:
The
ability to do work is called energy. Its SI unit is Joule and CGS unit is
calorie.
Primary
Source of Energy: The natural sources of energy which are used in the
same for as they are found in the nature. Solar energy, fire wood, coal,
natural gas, etc are the primary sources of energy.
Secondary
Sources of energy: The sources of energy which are derived from the
primary sources of energy are secondary sources of energy. Examples: Petrol,
diesel, hydroelectricity, charcoal, etc.
Renewable
sources of energy: The sources of energy which can be replenished in a
short period of time or never depleted are renewable sources of energy.
Example: Firewood, Hydro-electricity, solar energy, wind energy,
Non-renewable
Sources of energy: The sources of energy which once depleted cannot be
replaced in a short period of time. Example: Petrol, diesel, coal, natural gas,
etc.
The
Sun: An Ultimate Source of Energy: All the sources of energy present
on the earth are directly or indirectly derived from the sun i.e. solar energy.
For example: Coal is formed millions of years ago from the plants. The energy
present in coal was obtained from the sun by the process of photosynthesis in
the past.
The sun
has 57000Caverage temperature on its surface and its central core
has 1.5×107 0C temperature. It produces 4×1026J/S and
earth receives 1.4KW/m2.
Some
Non-renewable Sources of Energy:
Fossil
Fuel: The sources of energy which is formed from the remains of plants and
animals buried inside the earth's crust millions of years ago. Coal, petroleum
oil and natural gas are the fossil fuels.
a)
Coal: Coal is a
hard, black, solid form of fossil fuel formed by the fossilization of plants
and animals buried inside the earth's crust millions of years ago. Bituminous,
Sub-bituminous, lignite and anthracite are the grades of coal. Among them
anthracite is the highest graded coal.
b)
Petroleum oil or Mineral Oil: Mineral
oil is a fossil fluid trapped in the non-porous sedimentary rocks formed from
the decomposition of organisms that lived millions years ago. Example: Petrol,
diesel, kerosene, etc.
c)
Natural gas: Natural
gas is the gaseous form of fossil fuel which is the mixture of various form of
hydrocarbon such as methane, ethane, propane and butane. It is filled in the
cylinders at a very high pressure which can liquidify it. So, it is called
Liquidified petroleum gas (LPG).
Renewable
Sources of Energy:
Hydroelectricity:
Hydroelectricity is the energy generated by rotating turbine by using running
water with great speed. Nepal has the capacity to produce 83000 MW of
electricity.
Alternative
sources of energy: The renewable sources of energy which can be used
as an alternative source of energy in place of non-renewable and traditional
sources of energy are called alternative sources of energy. Example: Bio-mass,
hydropower, solar energy, wind energy, tidal energy, geo-thermal energy,
nuclear energy, etc
Nuclear
energy: The energy obtained as a result of nuclear reaction (either nuclear
fission or nuclear fusion) is called nuclear energy.
Nuclear
fusion: The nuclear reaction in which two or more lighter nuclei fuse together
to form a heavy nucleus with the release of enormous amount of energy is called
nuclear fusion reaction.
Thermonuclear
fusion reaction: The nuclear fusion reaction that takes place under
high temperature is called thermonuclear fusion reaction.
Nuclear
fusion reaction occur in sun, hydrogen bomb and stars are the examples of
nuclear fusion.
Thermonuclear
fusion reaction occur as follows:
Deuterium
Tritium
(light helium)
2He3+2He3 2He4+1H1+1H1+energy
41H1 2He4+21e0+
γ-radiation + energy
Nuclear
fission: The nuclear reaction in which a heavy nucleus of any radioactive element
splits into two or more lighter nuclei with the release of large amount of
energy is called nuclear fission. Example atom bombs, energy released from
nuclear power plants, etc.
A typical
reaction of nuclear fission reaction is as follows:
92U235+0n1 56Ba141+36Kr92+30n1+energy
Einstein's
mass energy relation: The equation E = mc^2 states
that the amount of energy possessed by an object is equal to its mass
multiplied by the square of the speed of light. Since the speed of
light is an incredibly high number, almost 300,000 km/sec, a small amount
of mass contains a lot of energy. Additionally, the equation suggests that
energy and mass are interchangeable with each other. In other words, energy can
be converted to mass and mass to energy.
Tidal
Energy: The energy produced due the fall and rise in water level in sea or ocean
is called tidal energy. The tidal energy is used to generate electricity.
Wind
energy: The energy possessed by high moving wind is called wind energy. The
kinetic energy of the wind can be converted into electrical energy by
connecting a generator/dynamo with the windmill.
Geothermal
energy: The heat energy present in the interior of the earth is called
geothermal energy. Geothermal energy can be converted into electrical energy.
Hot water springs, volcanic regions are the examples of the places where
geothermal energy is available.
Solar
energy: The energy radiated from the sun is called solar energy. It is the main
source of energy on the earth. It can be used to run different appliances like
heating devices (solar dryer, solar cooker), run electrical appliances using
solar panels, etc.
Energy
crisis: The scarcity of non-renewable sources of energy that is likely to happen
in future due to over exploitation of non-renewable sources of energy is called
energy crisis.
1.
Define thermonuclear fusion reaction.
The thermonuclear fusion reaction is a phenomenon in which the two
or more lighter reactive nuclei fuse together to form a heavier nucleus to
produce tremendous amount of energy in the course of nuclear reaction.
2.
What is the estimated temperature of the outer surface of the sun?
The estimated surface temperature of the sun is 57000C.
3.
What is energy crisis?
The state of shortage of source of energy that is likely to be
happen in near future due to excessive use of non-renewable sources of energy
is called energy crisis.
4.
What is alternative source of energy?
The energy that are to be developed instead of energy sources
frequently used and are cheaper and durable are called alternative sources of
energy.
5.
Define fossil fuel.
The fuel obtained from the remains of plants and animals buried
deep inside the earth crust millions of years ago such as coal, petroleum etc
is called fossil fuel.
6.
What is non-renewable energy source?
The sources of energy that are found to be accumulated in nature
over a very long time and cannot be quickly replaced when exhausted are called
non-renewable sources of energy. Coal, natural gas, petroleum oil are the
examples of it.
7.
Name the highest quality of coal.
Anthracite is the highest quality of coal.
8. What is hydro-power?
The electricity generated by rotating turbine with the help of
water is called hydropower.
9. Write any two conditions
required in the sun for nuclear fusion reaction.
Two conditions that are required for nuclear fusion reaction in
the sun are:
i) There is abundant amount of hydrogen in the sun,
ii) There is sufficient temperature and pressure in the sun to
carry out nuclear fusion reaction.
10. Write the names of any two radioactive
elements.
Uranium and Plutonium are the two radioactive elements.
11. What amount of average
energy does the earth receive per square meter?
The earth receives 1400 joules of energy per second per square
meter area in an average.
12. Write a major
disadvantage of fossil fuel.
Two disadvantages of fossil fuel are:
i) The stock of fossil fuel is limited.
ii) They cause environmental pollution.
13. Write any two natural
phenomenons from which geothermal energy can be obtained.
Two natural phenomenon from which geothermal energy can be
obtained are:
i) Volcanic eruption ii)
Hot water springs or hot spots
14. What is bio-fuel?
Any fuel derived from the organic matter like animal dung or
agricultural wastes (biomass) is called bio-fuel.
15. What is the source of
solar energy?
The main source of energy in the sun is thermonuclear fusion
reaction of hydrogen nucleus in the sun.
16. What is primary source
of energy?
The source of energy which is used in the naturally occurred form
are called primary sources. Coal, natural gas, cow dung, fire wood etc are the
examples of primary sources of energy.
17. What is renewable source
of energy?
A source of energy which can be renewed again and again within a
relatively short period of time is called a renewable source of energy.
18. What is biomass?
The waste matter of plants and animals that can be converted into
energy is called biomass.
19. What is geothermal
energy?
The heat energy obtained from the certain depth of the earth can
be used to generate energy called geothermal energy.
20. Write any two preventive
measures of energy crisis.
Two preventive measures of energy crisis are:
i) By using fuel energy wisely and economically,
ii) By promoting electrical vehicles in place of vehicles run by
fossil fuels.
iii) By promoting public vehicles in place of private vehicles.
21. Write any two ways which
reduces the energy crisis in Nepal.
In contest of Nepal, energy crisis can be reduced by adapting the
following measures:
i) As our country is agricultural country, so more priority should
be given for the use of biomass energy.
ii) Nepal has potentiality to produce 83000MW of electricity. So,
more priority should be given for the production and use of hydroelectricity.
22. Give two alternative
sources of energy.
Two alternative sources of energy are: Biomass and Solar energy
23. What is nuclear energy?
The energy released when two or more lighter nuclei fuses together
or a heavy nucleus undergoes fission to produce tremendous amount of energy in
the form of heat and light is called nuclear energy.
24. Give any two examples of
non-renewable source of energy?
Two examples of non-renewable sources of energy are: Coal and
Petroleum oil.
25. Write any two uses of
hydropower.
Two uses of hydropower are:
i) It is used to run vehicles like metro train, metro bus etc.
ii) It is used for various household purposes such as cooling,
heating, lightening, cooking, etc.
Group
B
26. Justify by giving two
points that use of hydropower should be increased rather than that of coal and
mineral oil for energy.
The use of hydropower should be increased rather than that of coal
and mineral for energy due to the following reasons:
a)
Coal and mineral oil are
non-renewable sources of energy where as hydropower is the renewable source of
energy.
b)
The coal and mineral oil
are developed in long duration from the decomposition of the living things but
hydropower is generated from the flow of water.
27. Write any two advantages
of mineral oil.
Two advantages of mineral oil are:
a)
It is cheap and easily
available than other fuel.
b)
They are easy to
transport from one place to another.
28. Sun is also called the
atomic power plant, why?
The sun generates energy from the thermonuclear fusion reaction of
atoms of hydrogen. It takes place in extreme high temperature and pressure
inside the sun. In thermonuclear fusion reaction hydrogen atoms combine
together to form deuterium and deuterium combines with hydrogen atom to form
tritium and finally tritium reacts together to form helium with the release of
tremendous energy like an atomic reactor. So, the sun is also called atomic
power plant.
29. Write ay two reasons
that urbanization brings energy crisis.
Two reasons that the urbanization brings energy crisis are:
a)
With the urbanization,
the demand of fossil fuel and other sources of energy increases as the number
of vehicles, population and industries are more in urban area.
b)
The living standard of
urban people is more that rural area. Hence, the consumption of fossil fuel is
more in urban area.
30. In the present world,
the use of hydroelectricity is increasing. Write any two reasons.
In the present world, the use of hydroelectricity is increasing.
Two reasons for it are:
a)
Hydropower is renewable
source of energy and it can be generated continuously for many years.
b)
It is pollution free
source of energy.
31. How is enormous energy
produced due to decomposition of Uranium?
When 92U235 radioactive element uranium is
bombarded with a slow moving neutron in a nuclear reactor, it undergoes nuclear
fission reaction and it breaks down into 56Ba141 and 36Kr92
and 3 neutron with the release of tremendous energy. The reaction is as
follows.
92U235+0n1 56Ba141
+ 36Kr92+30n1+Q (energy)
32. Suggest three reasons
which help to solve the problem of energy crisis. Name three alternate sources
of energy that are suitable in Nepal.
Three reasons which help to solve the problem of energy crisis
are:
a)
By using fuel wisely and
economically;
b)
By promoting electrical
vehicles in place of vehicles run by fossils fuels.
c)
By developing
alternative sources of energy.
Three
alternate source of energy that are suitable in Nepal are: i) Solar energy ii)
Biofuel
33. Name any one renewable
energy. Hydropower is more useful than coal, why?
Same as 32 . Hydropower is more useful than coal due to the
following reasons:
a)
Hydropower can be
converted in any form of energy by using suitable instruments but not coal.
b)
Hydropower is pollution
free but coal causes pollution.
34. Justify with two reasons
that the hydroelectricity is the best alternative source of energy in context
of Nepal.
Hydroelectricity is the best alternative source of energy in
context of Nepal due to the following reasons:
a)
Nepal is rich in water resources
and it has potentiality to generate 83,000 MW of electricity.
b) It is pollution free and it does not cause any harm to
environment.
35. Mention any two remedial
measures to control energy crisis. Which of the following are non-renewable
sources of energy: mineral oil, hydroelectricity, tidal energy and coal.
Same as 21. Non-renewable sources of energy are mineral oil and
coal.
36. Write any two major
cause of using fossil fuel in the present context.
Two major causes of using fossil fuel in the present context:
a)
It is cheaper source of
energy.
b)
It is easy to transport.
37. Why should energy be
conserved? Write nay two methods to conserve energy at home.
Energy should be conserved because the excessive use of
non-renewable sources of energy may cause energy crisis in the near future. So
to save such energy sources the conservation of energy.
38. In context of Nepal both
bio-fuel and solar energy are useful. Out of these two sources of energy, which
one will be more useful? Justify your answer giving two points.
Out of bio-fuel and solar energy, bio-fuel is more useful in
context of Nepal.
a)
As Nepal is an
agricultural country, a lot of solid waste from field and animal dung can be
utilized into energy.
b)
It can be used for both
cooking and lightening.
39. What is the main cause
of energy crisis in Nepal? Write any one measure to solve it.
The main cause of energy crisis in Nepal is that there is no any
place in Nepal where mining of non-renewable sources of energy is done. As a
result there is no any source of petroleum and natural gas in the country. In
order to solve energy crisis in Nepal the following measures can be adapted;
a)
By giving more priority
to the biomass energy as our country is an agricultural country.
b)
By giving more priority
to hydroelectricity as our country is the second richest country in the water
resources.
40. In context of Nepal, use
of solar energy should be highly prioritized, why? Write any two reasons.
In context of Nepal, use of solar energy should be highly
prioritized due to the following reasons.
It is renewable sources of energy.
41. Write any two causes of
energy crisis.
Two causes of energy crisis are:
a)
Extremely increase in
the consumption of energy sources due to the population growth.
b)
The earth contains
limited supply of fossil fuels, like coal and mineral oil. These sources of the
earth are being used up at rapid rate.
42. How the consumption of
non-renewable energy can be reduced in our country? Write any two methods.
Same as 40.
43. For what two natural
processes is the solar energy being used?
Solar energy is used for the following natural processes:
a)
Circulation of water
cycle
b)
Blowing of wind
44. Fossil fuel energy is
also a form of solar energy, how? Use of hydropower should be increased instead
of coal and mineral oil, why?
The plants use solar energy to synthesize food which is stored in
different parts of their body. After their consumption, the solar energy are
transferred to the animals. Fossil fuel are formed from the remains of dead
plants and animals buried inside the earth after millions of years. Thus, the
energy present in fossil fuel is the outcome of solar energy. In other words,
fossil fuel is also a form of solar energy.
45. Government of Nepal
encourages the farmers to establish bio-gas plant. Write two reasons.
Government of Nepal encourages the farmers to establish bio-gas
plant because of the following reasons.
a)
Bio-gas is a alternative
renewable source of energy and are replenishable in nature.
b)
The raw materials are
easily available in the village and are cheap.
46. The higher priority has
been given for the use of biogas energy in Nepal. Give two reasons.
Same as above:
47. Hydroelectricity is an
indirect source of solar energy. Clarify this statement.
Hydroelectricity is generated by running water. Water in the river
is either formed by the melting of ice or raining. For the melting of ice,
solar energy is needed. Similarly, for raining water of the ocean must be
evaporated which is only possible due the presence of solar energy.
Hydroelectricity is an indirect source of solar energy.
48. It is difficult to
produce hydroelectricity in Nepal. Give two reasons.
It is difficult to produce hydroelectricity in Nepal. Two reasons
for it are:
a) The geographical structure of Nepal is mountainous. There are a
lot of landslide and mudslide regions in hills and mountains. The establishment
of hydropower station is not suitable everywhere in the country.
b) There is lack of skilled manpower an sufficient economy in the
country.
49. The use of solar energy
should be increased in the context of Nepal. Give two reasons to justify this
statement.
The use of solar energy should be increased in context of Nepal.
Two reasons for it are:
a)
It is renewable source
of energy which is long lasting (about 25-30 years) source of energy.
b)
It is not possible to
generate electricity or transfer electricity to all regions of the country as
Nepal landform is mountainous. So, solar energy is best suited in such places.
50. What type of energy is
coal? Why more preference is given for the development of alternative sources
of energy in the world? Write two reasons.
Coal is a non-renewable source of energy. More preference is given
for the development of alternative sources of energy in the world because of
the following reasons.
a)
Non-renewable sources of
energy are limited in the nature which is depleting continuously.
b)
To overcome the energy
crisis in the future.
51. Write two differences
between nuclear fusion and nuclear fission.
Two differences between nuclear fusion and nuclear fission are:
|
Nuclear fusion |
Nuclear fission |
|
1. Two lighter nuclei combine together to form a single heavy
nucleus. |
1. A heavy nucleus splits into two or more nuclei with the
release of energy. |
|
2. Hydrogen bomb is based on nuclear fusion. |
2. Atomic bomb is based on nuclear fission. |
|
3. For nuclear fusion high pressure and temperature is required |
3. For nuclear fission high pressure and temperature is not
necessary |
52. Repeated
53. Mention any four major
ways to solve energy crisis.
Four major ways to solve
the problem of energy crisis are:
a)
By using fuel wisely and
economically;
b)
By promoting electrical
vehicles in place of vehicles run by fossils fuels.
c)
By developing
alternative sources of energy.
d)
By promoting public
vehicle in place of private vehicles.
54. Give any two reasons
that the sun is considered as the main source of energy.
Two reason, that the sun is considered as the main source of
energy are:
a)
The sun provides energy
for all living beings directly or indirectly.
b)
The alternative sources
of energy like wind, hydropower, geothermal etc are indirectly derived from
solar energy.
55. Fossil fuel is known as
non-renewable source of energy, why?
Fossil fuel is known as non-renewable source of energy because its
stock is limited in nature and can not be regain in short period of time once
it is depleted from the nature.
56. Write two differences
between renewable and non-renewable sources of energy.
Two differences between renewable and non-renewable sources of
energy are:
|
Renewable sources |
Non-renewable sources |
|
1. These sources of energy are
produced continuously in the nature and can't be exhausted. |
1. These sources of energy are
stored in nature and can not be replaced quickly if exhausted. |
|
2. They are present in great
amount like water, wind, sun-light, etc. |
2. These are present in scarce
amount in nature like coal, petroleum, etc. |
Group C
57. Write the thermonuclear
fusion reaction that takes place inside the core of the sun. OR How is energy
produced in the sun? Explain with chemical reaction.
At first two hydrogen atoms combine to form a deuterium and energy
is released. Then the deuterium combines with one hydrogen to form Helium-3,
and energy is released. Further two Helium-3, combines to form a helium on
release of energy. Overall four hydrogen atoms combine to form a helium and
high amount of energy is liberated by nuclear fusion in the sun.
1H1+ 1H1 1H2
+ 1e0 + energy
1H2+ 1H1 2He3
+ energy
He3+ 2He3 2He4 + 1H1
+1H1 + energy
1H1+1H1+1H1+1H1 2He4 + 2e0 + energy
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