SOURCES OF ENERGY
KEYNOTES
KEYNOTES
• Conditions of the good fuel
(i) High calorific value
(ii) Less smoke
(iii) Less residue left after burning
(iv) Easy available
(v) Inexpensive
(vi) Easy to store and transport
• Conventional sources of energy
• FOSSIL FUELS: Millions of years ago plants and animals tissues got buried under the ground and were subjected to high temperature and pressure. Coal is a fossil fuel which was formed due to subjection of plant tissues under high pressure and temperature. While petroleum is obtained from the remains of animals between sedimentary rocks.
These are non-renewable sources of energy and lead to pollution on combustion.
• THERMAL POWER PLANT: -Thermal power plant use coal, petroleum and natural gas to produce thermal electricity.
-The steam produced is used to run the turbine to generate electricity.
- Electricity transmission is more efficient.
Disadvantages
• Fossil fuels are used which is non- renewable source of energy.
• Leads to water and air pollution.
• HYDRO POWER PLANTS
It is themost conventional renewable source obtained from water falling on from the height
• It Is clean non- polluting source of energy
• Dams are constructed near rivers. As the water level rises, the kinetic energy of water gets changed to potential energy
• The water is released to rotate the turbine and electricity is generated.
Disadvantages
• Highly expensive
• Dams can be made at limited areas
• Large areas of human habitation and agricultural fields are submerged
• Problem of rehabilitation of displaced people
• NON CONVENTIONAL SOURCES OF ENERGY
• WIND ENERGY: - It can be converted to mechanical and electrical energy
• Kinetic energy of wind is used in lifting water from pump, grinding grains etc.
ADVANTAGES
• Eco friendly
• Renewable
DISADVANTAGES
• Wind speed is not uniform
• Need large areas for wind mills
• Need lot of investment
• Output is less
• SOLAR ENERGY: - Solar radiations can be converted to other forms of energy through photovoltaic cells.
• These cells convert solar radiations directly into electricity through silicones solar cells.
• Solar cookers are painted black from outside and a have glass plate to trap solar radiations by greenhouse effect.
ADVANTAGES
• Eco friendly
• Renewable
• Used in rural areas
DISADVANTAGES
• Silicon cells are expensive
• Solar radiation are not uniform over earth’s surface
• Can’t be used at night or on cloudy day.
• Maximum temperature achieved by solar cooker is 100° C
• GEOTHERMAL ENERGY
Utilization of heat in the interior of earth for power generation is called geothermal energy. In places where hot springs or geysers occur steam trapped in rocks is brought in turbine through pipes to generate electricity.
ADVANTAGES
• Renewable
• Inexpensive
DISADVANTAGES
• Only available in few sites
• NUCLEAR ENERGY
Radioactive elements generate large amount of energy e.g. 1 ton of U-235 provide as much as energy as 3 million ton of coal.
It is sued for heat generation and as fuel for marine vessels.
ADVANTAGES
• Alternative source due to depletion of fossil fuels
• From small amount of fuel large amount of energy is obtained
DISADVANTAGES
• Risk of nuclear wastage
• High cost
• Pollution
ENERGY FROM THE SEA
• Tidal energy: depends upon the harnessing of rise and fall of the sea level due to tidal energy. Dams are constructed across a narrow part of sea and turbine converts tidal energy to electricity
• Ocean thermal energy: the difference in temperature of water at surface and the water at the depths is exploited. The warm surface water is used to boil ammonia and turbine is run by the vapours of ammonia.
WAVE ENERGY
• Waves of sea are used as their kinetic energy is converted into electrical energy
• Turbine is used to produce electricity
Class X Science
NCERT Solution for Sources of Energy
NCERT Solution for Sources of Energy
NCERT IN-TEXT QUESTIONS SOLVED
1. What is a good source of energy?
Ans. The energy which is easily available, cheap, does not produce pollution is said to be good source.
2. What is a good fuel?
Ans. A good fuel is one which is cheap, easily available, easy to handle, transport, has proper ignition temperature and high calorific value.
3. If you could use any source of energy for heating your food, which one would you. us? and why?
Ans. If sun�s ,heat is accessible then solar cooker or else CNG.
4. What are the disadvantages of fossil fuels?
Ans. Disadvantages of fossil fuels are:
(a) They are non-renewable resources
(b) They cause pollution which can lead to
(i) Acid rain
(ii) Smoke
(iii) Green house effect due to CO2
(iv) Fly ash suspended in air.
5. Why are we looking at alternate sources of energy?
Ans. The sources of energy we are using now is fossil fuel i.e., petrol and petroleum products, and coal which are exhaustible and non-renewable. The demand of energy is increasing due to increased population and better technology that has added many machines, appliances to add comfort to life style. Hence ,the. demand for energy is increasing day by day. To overcome this problem we are looking for alternate sources of energy.
6. How has the traditional use of wind and water energy been modified for our convenience?
Ans. (i) The traditional use of water energy has been modified and we have built dams, turbines and dynamos to generate electricity with the help of flow of water.
(ii) Wind; energy is used to rotate the wind mills, turbines and generate electricity by constructing wind fans.
7. What kind of mirror-concave, convex or plain-would be best suited for use in a solar cooker? Why?
Ans. Concave minor would be best suited for use in solar cooker. As it is a converging mirror and would converge sun�s heat radiation at one focussed point.
8. What are the limitations of the energy that can be obtained from the oceans?
Ans. The limitations of ocean energy are:
(i) Few limited sites/places where this wave, tidal or ocean thermal energy can be obtained.
(ii) The cost of construction of plants is very; high
(iii) The efficiency of producing energy is also low
9. What is geothermal energy?
Ans. The heat energy obtained in the form of steam from under the earth�s crust is called geothermal energy
10. What are the advantages of nuclear energy?
Ans. The advantages of nuclear energy are:
(i) A very small amount of radioactive material can produce large amount of energy which can be controlled and converted into usable form e.g., 1 kg Uranium = 25 thousand tonnes of coal.
(ii) It does not release any smoke or harmful gases in the air. Hence it can, curbthe global warming that is caused due to green house effect.
11. Can any source of energy be pollution free? Why or why not?
Ans. Yes, there can be a source of energy that can be pollution free in using it. e.g., sun�s energy that is used in solar cooker, solar water heater, solar cell panels.
12. Hydrogen has been used as a rocket fuel. Would you consider It a cleaner fuel than CNG? Why or why not?
Ans. Hydrogen is a cleaner fuel than CNG because hydrogen on burning/combustion form water whereas CNG that contain methane burns to produce carbon dioxide.
13. Name two energy sources that you would consider to be renewable. Give reasons fur your choices.
Ans. Solar energy-it will not get exhausted it can be used for multipurpose-heating, burning and producing electricity. It will not cause any pollution, it is cheap and easily available.
Energy from water-Energy can be obtained from water in various form i.e., for producing electricity without pollution.
QUESTIONS FROM NCERT TEXTBOOK
1. A solar water heater cannot be used to get hot water on
(a) a sunny day. (b) a cloudy day. (d) a windy day. (c) a hot day.
Ans. (b) a cloudy day.
2. Which of the following is not an example of a bio-mass energy source?
(a) wood (b) gobar-gas (c) nuclear energy (d) coal
Ans. (c) nuclear energy.
3. Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun�s energy?
(a) geothermal energy (b) wind energy
(c) nuclear energy (d) bio-mass
Ans. (c) nuclear energy.
4. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Ans.
| Sun | Fossil fuels |
| 1. It is renewable source of energy. | It is non-renewable source of energy. |
| 2. It does not cause pollution. | It causes pollution in the environment. |
| 3. It is cheap, easily available for most of the time and at most of the places. | It is expensive, not easily available ai1y time and anywhere. |
5. Compare and contrast bio-mass and hydro electricity as sources of energy.
Ans.
| Bio-mass as Energy Source | Hydro electricity as Energy Source |
| 1. It causes pollution. | It does not cause pollution. |
| 2. It is cheap and easily available. | It is expensive and not easily available. |
| 3. Initial cost for building the bio-gas plant is very cheap and its maintenance is also cheap. | The initial cost of building the power plant is expensive, its maintenance is also expensive. |
6. What are the limitations of extracting energy from:
(a) the wind? (b) waves? (c) tides?
Ans. (a) The Wind
(i) It can be extracted only at limited sites where the wind blows most of the time in a year.
(ii) The minimum speed of wind should be 15 km/h.
(iii) Large area is required to build the wind farm/wind mills which is expensive affair.
(iv) Efficiency, is low.
(b) Waves
(i) The place and time is limited when the waves are strong.
(ii) Initial setup cost is expensive.
(iii) Efficiency is low.
(c) Tides
(i) The areas where tidal energy can be harnessed is less.
(ii) The efficiency is very low.
(iii) The plants are not cost effective.
7. On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Ans. Both (a) and (b) options are same:
| Renewable/Inexhaustible | Non-renewable/Exhaustible |
| 1. They are also called inexhaustible | They are also called as exhaustible |
| 2. The energy source that will not finish and can be renewed or made again and again is called renewable source of energy e.g., sun, wind, water. | The energy source that will finish and will get exhausted and cannotrbe made very soon or takes million of years for its formation e.g., fossil fuels-petrol, coal. |
8. What are the qualities of an ideal source of energy?
Ans. he ideal source should have the following qualities:
1. should be cheap, easily available and easy to handle.
2. It can be transported easily.
3. It should have high calorific value.
4. It should have proper ignition. temperature.
5. It should not cause any environmental pollution.
9. What are the advantages and disadvantages of using a solar cooker.? Are there places where solar cookers would have limited utility?
Ans. Advantages of solar cooker:
(a) It is cheap and easy to handle.
(b) It does not need any fuel for cooking food.
(c) It is pollution free.
Disadvantages of solar cooker:
(a) It is very slow, takes long time for cooking.
(b) It is dependent on sun�s light, cannot work on cloudy day.
(c) The reflectors position need to be monitored so as it reflects the sunlight at the centre focused point of the solar cooker.
Yes-the places where sun�s energy not sufficient, the use of solar cookers would be limited
10. What are the environmental �consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans. Due to increasing demand of energy the available sources of energy are depleting at fast rate. The use of fuels on large scale is releasing lot of gases and unwanted particles in the air. The gases like SO2, NO2 are causing acid rain that is destroying monuments, iron articles, bridges etc. The CO2 released in air is causing green house effect that is leading to global warming which will melt the ice and sea-level will increase submerging coastal areas and islands. To reduce energy consumtion we should look for alternative source of energy which can help us to overcome all these problems.
SOURCES OF ENERGY
PREVIOUS YEAR QUESTIONS
PREVIOUS YEAR QUESTIONS
1. Which force is responsible for stability of our universe?
1. Name one fuel used in nuclear reactor. (CBSE CCE 2012)
2. Name the reaction responsible for large energy production in the sun. (CBSE CCE 2012)
3. How has the traditional use of wind energy been modified for our convenience? (AI 2008C)
4. Biogas is considered to be a boon to the farmers. Give reasons. (CBSE CCE 2011)
5. What is a solar cell panel? Mention any three of its applications? (CBSE CCE 2012)
6. Why are many thermal plants set up near coal or oil fields? (AI 2008C)
7. Distinguish between renewable and non-renewable resources of energy. Also give examples (CBSE CCE 2011)
8. What is geothermal energy? What are the advantages of wind energy? (CBSE CCE 2011)
9. Name the device used to convert
a. Solar energy into heat
b. Solar energy into electricity (DELHI 2006C)
10. Write the principle of generation of electric power by a boiling water type nuclear reactor. Name the coolant used in such a reactor. (DELHI 2005C)
11. a. name four gases which are mainly present in biogas.
b. List two advantages of using biogas over fossil fuels. (AI 2006C)
12. List any three hazards of nuclear waste. How does the disposal of nuclear waste pose a problem for the plant and animal life? (CBSE CCE 2012)
SOURCES OF ENERGY
TEST
TEST
Time: 1 hour Maximum Marks: 30
1. What is the nuclear fission process? [1]
2. Name any two gases, which are major constituents of biogas. [1]
3. What is a solar cell panel? [1]
4. Give the names of any two devices that utilize solar energy. [1]
5. Outline the energy conversion that takes place in a hydro power plant. [1]
6. Why can CNG be considered as an environment friendly fuel? [1]
7. Define anaerobic degradation. [1]
8. What is the typical range of voltage and power of a solar cell, when exposed to the sun? [1]
9. What is the condition under which ocean thermal energy can be trapped and used? [1]
10. What is the cause of geothermal energy? [1]
11. Define bio�mass. Give two examples. [2]
12. What are the limitations of using wind energy?[2]
13. Why is it difficult to use hydrogen as a source of energy? [2]
14. What is acid rain? What are its harmful effects? [3]
15. What characteristics should an ideal fuel possess? [3]
16. Give the advantages and disadvantages of solar cell panels. [3]
17. (i) What is the use of black painted surface in a solar cooker? [5]
(ii) What is the unit in which nuclear energy is expressed? How is it related to joule?
(iii) Give the disadvantage of generating hydro�electricity.
OR
Discuss the working of a hydro power plant using a labeled diagram.
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