Sources of Energy- Lakhmir Singh Manjit Kaur Solutions Pg No. 156 Class 10 Physics

Solutions of Sources of Energy- Lakhmir Singh Manjit Kaur VSAQ, SAQ, LAQ and MCQ Pg No. 156 Class 10 Physics

Solutions of Sources of Energy- Lakhmir Singh Manjit Kaur VSAQ, SAQ, LAQ and MCQ Pg No. 156 Class 10 Physics

Very Short Answer Type Questions-Pg-156

1. What type of nuclear reaction is responsible for the liberation of energy:
(a) In a nuclear reactor?
(b) In the sun?

Answer

→ (a) Nuclear fission-Nuclear fission is a process where the nucleus of an atom is split into two or more smaller nuclei, known as fission products.

b) Nuclear fusion-nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles.

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

Answer

→ Neutrons of uranium-235 are utilized to cause further fission of its nuclei. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy.

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

Answer

→ Neutrons bring about the fission of uranium-235.

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

Answer

→ The fission of uranium-235 is caused by low energy neutrons because a fast neutron will not be captured, so neutrons must be slowed down by moderation to increase their capture probability in fission reactors.

5. Name the type of nuclear reaction which is involved in the working of:
(a) A hydrogen bomb.
(b) An atom bomb.

Answer

→ (a) Nuclear fusion-It's a mixture of deuterium and tritium (both of them rare forms of hydrogen) for nuclear fusion.
(b) Nuclear fission-It's either uranium or plutonium for fission bombs.

6. Name the moderator used in a nuclear reactor.

Answer

→ Commonly used moderators include regular (light) water (roughly 75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors).

7. Of what material are the control rods of a nuclear reactor made?

Answer

→ Control rods of a nuclear reactor are made of boron. Control rods are used in nuclear reactors to control the fission rate of uranium and plutonium.

8. What do you think is the purpose of the thick, concrete chamber surrounding the reactor of a nuclear power plant?

Answer

→ Nuclear reaction produces heavy hazardous radiations in the nuclear power plants. Hence, thick concrete chamber is required to prevent the radioactive rays to travel outside.

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

Answer

→ Uranium is used up in the reactors in a nuclear power station.

10. State one use of nuclear fission reactions.

Answer

→ Nuclear fission is used to generate electricity, for the destructive component of nuclear weapons and to break down radioactive elements into other elements.

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

Answer

→ Million electron volt (MeV) is used for expressing the energy released in nuclear reactions.

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

Answer

→ 1 atomic mass unit=931 MeV, where MeV stands for Million electron Volt.

13. Fill in the following blanks with suitable words:
(a) Splitting of a heavy nucleus into two lighter nuclei is called .............
(b) Uranium-235 atoms will split when hit by ............ This is called ....................
(c) Nuclear ................ is used in nuclear power stations for the production of electricity.
(d) In a nuclear power station, nuclear fission takes place in the .............

Answer

→ (a) Nuclear fission
(b) Neutrons; nuclear fission
(c) Fission
(d) Reactor

Short Answer Type Questions-Pg-157

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

Answer

→ Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei).The fission process often produces free neutrons and photons (in the form of gamma rays), and releases a large amount of energy.

E.g., When uranium-235 atoms are bombarded with slow moving neutrons, the heavy uranium nucleus breaks up to produce two medium-weighted atoms and 3 neutrons, with the emission of tremendous amount of energy.

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

Answer

→ The process that fuels our sun and allows it to give off that much energy is called nuclear fusion. Nuclear fusion is a reaction where two atomic nuclei fuse together to create a larger nucleus and in the process release energy.
When deuterium atoms are heated to an extremely high temperature under extremely high pressure, then two deuterium nuclei combine together to form a heavy nucleus of helium, and a neutron is emitted. A tremendous amount of energy is liberated in the process.

15B. Why are very high temperatures required for fusion to occur?

Answer

→ For a nuclear fusion reaction to occur, it is necessary to bring two nuclei so close that nuclear forces become active and glue the nuclei together. This is the reason why nuclear fusion reactions occur mostly in high density, high temperature environment.

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.

Answer

→ Hydrogen gas is the nuclear fuel in the sun. The sun can be assumed as a huge thermonuclear furnace where hydrogen atoms continuously get fused into helium atoms. Hence, the mass during these fusion reactions gets lost and as a product energy is being produced.
Nuclear reaction:
41H1  4He2 + 20e1 + tremendous amount of energy.

17A. Write Einstein's mass-energy equation. Give the meaning of each symbol which occurs in it.

Answer

→ Einstein's mass-energy equation is, E=mc2,
The equation is derived directly from Einstein’s Special Theory of Relativity
Each of the letters of E = mc2 stands for a particular physical quantity. Writing them out in full we get:
E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
c = the speed of light (measured in meter per second, ms-1)

17B. If 25 atomic mass units (u) of a radioactive material are destroyed in a nuclear reaction, how much energy is released in MeV?

Answer

→ As,
1 atomic mass unit = 931 MeV
25 atomic mass unit
= 931 x 25 MeV
= 23275 MeV
Hence, 23275 MeV of energy is released.

18A. What is the source of energy of this sun and other stars?

Answer

→ The source of energy of this sun and other stars is nuclear fusion reactions of hydrogen. The net process is the fusion of four Hydrogen nuclei to make one helium nucleus plus some energy. The balance between gravity compression and outward thermal pressure controls the rate of the nuclear fusion reactions.

18B. Describe the working of a hydrogen bomb.

Answer

→ The hydrogen bomb consists of heavy isotopes of hydrogen called deuterium and tritium along with lithium-6. Atom bomb is used for the explosion of hydrogen bomb. While the atom bomb is exploded, since its fission reaction a lot of heat is produced which raises the temperature of deuterium and tritium to 107°C in a few microseconds. Then fusion reactions of deuterium and tritium take place which produces a tremendous amount of energy. This explodes the hydrogen bomb. Lithium-6 is used to produce more tritium needed for fusion.

18C. What is common between the sun and a hydrogen bomb?

Answer

→ The source of energy is same for both the sun and the hydrogen atom, that is nuclear fusion.

19A. What will happen if slow moving neutrons are made to strike the atoms of a heavy element 23592U? What is the name of this process?

Answer

→ When slow moving neutrons are made to strike the atoms of a heavy element uranium-235, the heavy uranium nucleus breaks up to produce two medium-weighted atoms and 3 neutrons, with the emission of tremendous amount of energy. This process is called nuclear fission..

19B. Write a nuclear equation to represent the process which takes place.

Answer



19C. Name one installation where such a process is utilized.

Answer

→ At nuclear power station such process are utilized.

20A. What are the advantages of nuclear energy?

Answer

→ Advantages of nuclear energy are as follows:
1. Expense
Less uranium is needed to produce the same amount of energy as coal or oil, which lowers the cost of producing the same amount of energy.
2. Reliability
When a nuclear power plant is functioning properly, it can run uninterrupted for up to 540 days.
3. No Greenhouse Gases
While nuclear energy does have some emissions, the plant itself does not give off greenhouse gasses.

20B. State the disadvantages of nuclear energy.

Answer

→ Disadvantages of nuclear energy are as follows:
1.Raw Material
Since, uranium is naturally unstable therefore special precautions must be taken during the mining, transporting and storing of the uranium.
2.Water Pollutant
The water that is pumped outside into nearby wetlands contains immense heat that can be damaging to eco systems located nearby the reactor.
3. If it has structural flaws or are improperly installed, a nuclear reactor could release harmful amounts of radiation into the environment during the process of regular use.

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 forever?
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?

Answer

→ a) Uranium-235 produces the energy in the fuel rods
b) No they won't last forever.
c) Energy is produced by nuclear fission.
d) In a nuclear reactor, a moderator is mixed with the uranium fuel to slow down the fast neutrons to the speed of thermal neutrons, which enables fission to occur in a controlled nuclear chain reaction.
e) Boron rods are used in nuclear reactors to control the fission rate of uranium and plutonium.
f) Liquid sodium or carbon dioxide gas is used as a 'coolant' to transfer the heat produced to heat exchanger for converting 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

Answer

→ (a) Graphite is used as a moderator.
(b) Concrete are used to absorb the radiations
(c) U-235 is used in control rods
(d) Boron can be used as control rods
(e) Liquid sodium 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?

Answer

→ a) In Nuclear reactors control rods are stick down into the fuel to absorb neutrons, to slow the reaction down, or withdraw to speed the reaction up.
b) Heat is removed from the nuclear reactor core with the help of liquid sodium. It absorbs the heat and transfers it to the heat exchanger. Then, this heat is used for converting water into steam in the heat exchanger, which is later used to produce electricity by rotating a turbine and its shaft which is connected to a generator.

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

Answer

→ On inserting the control rods in the graphite core, the rods begin absorbing the excess neutrons and maintain the rate of reaction as it is required . We can raise or lower the rods in the reactor from outside as per our requirement. The part which is present inside the reactor absorbs neutrons.

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

Answer

→ Advantages of nuclear energy:
i) It produces a large amount of useful energy from a very small amount of a nuclear fuel.
ii) Once the nuclear fuel is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need of feeding the fuel again and again.
iii) It does not produce gases like CO2 or SO2.

Disadvantages of nuclear energy:
i) The waste products of nuclear fission reactions are radioactive which keep on emitting harmful radiations for thousands of years and are difficult to store or dispose safely.
ii) Very high cost of installation is required.
iii) There is a limited availability of uranium fuel.

Long Answer Type Questions-Pg-157

26A. What is a nuclear reactor ? What is the fuel used in a nuclear reactor?

Answer

→ A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. U-235 is the fuel used in a nuclear reactor.

26B. With the help of a labelled diagram, describe the working of a nuclear power plant.

Answer

→ In a nuclear power plant, the fission of uranium-235 is carried out in a reactor R. Uranium-235 rods are inserted in a graphite core which acts as a moderator to slow down the neutrons. Boron rods B absorb excess neutrons and controls the rate of reaction. Liquid sodium or carbon dioxide gas, which is pumped continuously through pipes embedded in reactor by using a pump P, is used as a 'coolant' to transfer the heat produced to heat exchanger for converting water into steam. The hot steam at high pressure goes into a turbine chamber and makes the turbine rotate. The shaft of the generator also rotates and drives a generator connected to it.

26C. How is the working nuclear reactor of a power plant shut down in an emergency?

Answer

→ The working nuclear reactor of a power plant can be shut down in an emergency by inserting the control rods of Boron completely. They absorb all the neutrons, shutting down the reactor.

26D. Name five places in India where nuclear power plants are located

Answer

→ Five places in India where nuclear powerplants are located are:
(i) Tarapur
(ii) Kalpakkam
(iii) Narora
(iv) Kaprapur
(vi) kaiga

27A. Differentiate between nuclear fission and nuclear fusion.

Answer

→ Both fission and fusion are nuclear reactions that produce energy, but the applications are not the same. Fissions the splitting of a heavy, unstable nucleus into two lighter nuclei, and fusion is the process where two light nuclei combine together releasing vast amounts of energy.

27B. 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?

Answer

→ (i) nuclear fission
(ii) nuclear fusion

27C. Which produces more energy: nuclear fusion or nuclear fission?

Answer

→ Among both the process nuclear fusion produces more energy.

27D. Calculate the energy released in joules when 5 g of a material is completely converted into energy during a nuclear reaction.

Answer

→ Mass of material,
m = 5g = 0.005kg,
Speed of light, c = 3 x 108m/s
We know that, E = mc2
E = 0.005 x (3 x 108)2
E = 4.5 x 1014J
Hence, energy released= 4.5 × 1014J.

27E. How much is this energy in Me V? (Speed of light= 3 x 108 m/s)

Answer

→ The energy in MeV is given by:


(Since 1 MeV = 1.6 × 10–13 J)
= 2.8 × 1027 MeV.

Multiple Choice Questions (MCQs)-Pg-158

28. 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

Answer

→ Graphite is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions.

29. The control rods used in the reactor of a nuclear power plant are made of :
A. steel
B. graphite
C. uranium
D. boron

Answer

→ Because boron is capable of absorbing many neutrons without itself fissioning.

30. The 'coolants' which can be used in the reactor of a nuclear power station are:
A. liquid mercury and nitrogen dioxid
B. liquid sodium and carbon dioxide
C. liquid ammonia and carbon monoxide
D. liquid boron and uranium oxide.

Answer

→ A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction.

30. The 'coolants' which can be used in the reactor of a nuclear power station are:
A. liquid mercury and nitrogen dioxid
B. liquid sodium and carbon dioxide
C. liquid ammonia and carbon monoxide
D. liquid boron and uranium oxide.

Answer

→ A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction.

31. 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.

Answer

→ A nuclear reactor coolant is a coolant in a nuclear reactor used to remove heat from the nuclear reactor core and transfer it to electrical generators and the environment.

32. Which of the following is ultimately not derived from the sun's energy (or solar energy)?
A. wind energy
B. nuclear energy
C. biomass energy
D. ocean thermal energy

Answer

→ Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant.

33. One atomic mass unit (u) is equivalent to an energy of :
A. 931 eV
B. 9.31 MeV
C. 1 MeV
D. 931 MeV

Answer

→ 1 a.m.u is defined as 1/12th of the mass of an atom of 6C12 isotope. Hence a change in mass of 1a.m.u (called mass defect) releases an energy equal to 931 MeV.1 amu = 931 MeV is used as a standard conversion.

34. 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

Answer

→ In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).

35. One eV (electron volt) of nuclear energy is equivalent to :
A. 1.6 X 10-14 J
B. 1.6 X 10-12 J
C. 1.6 X 10-19 J
D. 1.6 X 10-13 J

Answer

→ (W = qV )
= (1.6 x 10-19 C) x (1 J/C)
= 1.6 x 10-19 J)

36. Which of the following can be produced during the nuclear fission as well as nuclear fusion reactions ?
A. protons
B. deutrons
C. electrons
D. neutron

Answer

→ Nuclear Fusion and nuclear fission are similar in that they both release large amounts of energy.

37. 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

Answer

→ Nuclear fusion is sun's source of energy.

38. The energy produced by converting 1 gram mass of a nuclear fuel into energy completely is:
A. 9 X 1016 J
B. 9 X 1014 J
C. 9 X 1015 J
D. 9 X 1013 J

Answer

→ Nuclear fuel is a substance that is used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.

39. 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

Answer

→ Nuclear fusion converts Hydrogen gas into helium producing tremendous amount of energy.

40. An uncontrolled nuclear chain reaction forms the basis of:
A. Nuclear power plant
B. Hydrogen bomb
C. Thermal power station
D. Atom bomb

Answer

→ An atom bomb, known as the A-bomb for short, is a bomb that creates its devastating explosive force by the splitting of atoms' nuclei through a process known as nuclear fission.

41. One MeV of nuclear energy is equivalent to:
A. 1.6 x 10-13 J
B. 1.6 x 10-19 J
C. 1.6 x 10-16 J
D. 1.6 X 10-15 J

Answer

→ Nuclear energy is the energy obtained by manipulating the internal structure of atoms.

42. 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

Answer

→ Nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles.

43. 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
D. Highly radioactive

Answer

→ Nuclear Waste is radioactive and that is the primary cause of the negative effects on human health and bodies.

44. 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

Answer

→ Energy is released from fission and fusion because breaking and formation of bond takes place.

45. Which of the following can undergo nuclear fusion reaction?
A. Uranium
B. Deuterium
C. Barium
D. krypton

Answer

→ Deuterium (symbol D or 2H, also known as heavy hydrogen) is one of two stable isotopes of hydrogen.

Questions Based on High Order Thinking Skills (HOTS)-Pg-159

46. A nuclear reaction is represented by the following equation:

(a) Name the process represented by this equation and describe what takes place in this reaction.
(b) Identify the particle c and the number x of such particles produced in the reaction.
(c) What does E represent?
(d) Name one installation where the above nuclear reaction is utilized.
(e) What type of bomb is based on similar type of reactions?

Answer

→ (a) Nuclear fission in which large nucleus splits into two smaller nuclei with the release of energy, brought about by the absorption of a neutron.
(b) Particle c is neutron; x = 3
(c) E represents the Energy liberated
(d) The reaction is utilized in Nuclear Power Station

(e) Atom bomb is based on similar type of reaction called nuclear fusion.

47. A nuclear reaction is represented by the equation :

(a) Name the process represented by this equation and describe what happens during this reaction.
(b) Identify the particle c and the number x of such particles produced in the reaction.
(c) What does E represent?
(d) State two conditions under which such a reaction takes place.
(e) What type of nuclear bomb is based on similar reactions ?

Answer

→ (a) Nuclear fusion in which two smaller nuclei combine in order to form a bigger nucleus with the release of energy, brought about under the conditions of high temperature and pressure.
(b) Particle c is neutron; x = 1
(c) E is the Energy liberated
(d) Such reactions takes place user the two following conditions:
• Millions of degrees of temperature and
• Millions of pascals of pressure
(e) Hydrogen bomb is based on similar reaction.

48. The mass numbers of four elements A, B, C and Dare 2, 20, 135 and 235, respectively. Which one of them will be most suitable to make:
(i) an atom bomb, and
(ii) a hydrogen bomb?

Answer

→ (i)D with a Mass number of 235
(ii) A with a Mass number of 2.

49. A nuclear power plant is working normally. What would you do it the reactor core suddenly got too hot?

Answer

→ If the reactor core all of a sudden gets too hot then it indicates that the rate of nuclear fission is intensified excessively so in order to reduce the rate of nuclear fission process insert the control rods of boron a little more into the reactor and hence the reactor would start working normally.

49. A nuclear reactor has half the length of all its control rods inserted in graphite. What must be done so that the reactor produces more heat? Explain your answer.

Answer

→ If such circumstances happens then we would withdraw the control rods a little more from inside the reactor. Doing this will increase the rate of nuclear fission process and hence would produce more heat .

50. Explain why, in a nuclear reactor, the chain reaction stops if the control rods are fully inserted into the graphite.

Answer

→ In a nuclear reactor, the chain reaction stops if the control rods are fully inserted into the graphite because the control rods absorb all the neutrons, and hence stopping the nuclear chain reaction.

Very Short Answer Type Questions-Pg-161

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

Answer


→ Hydrogen fuel is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG. On the other hand, hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Hence, hydrogen is cleaner than CNG.

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

Answer

→ CFLs are more energy efficient as they last from 8-10 times longer, use about 75% less energy, and produce 90% less heat while delivering more light per Watt.

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

Answer

→ Coal is expected to last for about 200 years,
Petroleum is expected to last for 40 years and
Natural Gas may last for 60 years.

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

Answer

→ Solar cooker and pressure cooker can be utilized for the cooking of food so as to save fuel as they use less energy to cook food in comparison of others.

Short Answer Type Questions-Pg-161

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

Answer

→ Factors which we should keep in mind while choosing a source of energy are:
It should do a large amount of work per unit mass or volume - it means that the output energy must be more than the input energy. It should have high calorific value.
It should be easily accessible - the energy source should be able to provide energy over a long period of time. Example: coal and petroleum.
Should be easy to store and transport - most common sources of energy such as coal, petrol and LPG need to be transported to users from their points of production. They also need proper storage. Thus it is important to store and transport these sources safely and economically.

Safe and convenient to use - energy sources should be safe as it is used by a large number of people and should be convenient.

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

Answer

→ No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly.
Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.

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

Answer

→ The increasing demand for energy is largely being met by the use of fossil fuel - coal and petroleum. But these fuels are exhaustible and non-renewable sources of energy. Moreover, burning of fossil fuels causes air pollution. Release of acidic oxides leading to acid rain affects our water and soil resources. These gases also produce greenhouse effect leading to rise in temperature. Then, there is a problem of disposal of ash produced due to burning of coal. Thus, our environment is being degraded.

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

Answer

→ To reduce energy consumption:
● we should lead a simple and a natural life. As an example, instead of using an air conditioner in a closed room we should live in an airy room having appropriate number of windows.
● Turn your monitor off at night and ditch the screensaver.
● Use LED bulbs as LED bulbs use 75% less electricity than incandescent bulbs.

Multiple Choice Questions (MCQs)-Pg-161

9. The major cause of environmental pollution is the use of :
A. Hydrogen as fuel
B. Biomass energy
C. Ocean energy
D. Fossil fuels

Answer


→ Gases released by the burning and combustion of fossil fuels include carbon monoxide, nitrogen oxides, sulfur oxides and hydrocarbons. In the air, these gases become a carcinogen, which can be inhaled and can also mix with falling rain to form acid rain.

10. The world's known coal reserves are expected to last for about:
A. 200 years
B. 400 years
C. 500 years
D. 100 years

Answer

→ Ultimate reserves designates all the coal that can eventually be mined in a given zone (that can be the whole planet).

11. 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

Answer

→ Petroleum is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth's surface, which is commonly refined into various types of fuels.

12. An energy efficient device for producing light is :
A. DLF
B. CFL
C. FCL
D. LPG

Answer

→ CFLs use much less energy than incandescent lamps.

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