Solutions of Sources of Energy- Lakhmir Singh Manjit Kaur VSAQ, SAQ, HOTS and MCQ Pg No. 148 Class 10 Physics
1. What substance is obtained as a residue when wood is burned in a limited supply of air?
Answer
→ Charcoal is obtained as a residue when wood is burned in a limited supply of air.
2. Name one source of energy which is not derived from solar energy directly or indirectly.
Answer
→ Geothermal energy is neither derived from the sun directly or indirectly. It is the heat present inside the earth.
3. What name is given to the heat energy obtained from hot rocks inside the earth?
Answer
→ Geothermal energy is the heat energy obtained from hot rocks inside the earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
4. Name the agent which decomposes animal dung into biogas.
Answer
→ Anaerobic bacteria decomposes animal dung into biogas. It digests the animal dung into a closed system and produces the biogas.
5. Which component of biogas is used as a fuel?
Answer
→ Biogas contains 54-70% of methane which is used as a fuel.
6. Name the constituents of biogas.
Answer
→ The constituents of biogas are mentioned below along with their % Constitution:
Methane: 54 – 70%
Carbon dioxide: 27 – 45%
Nitrogen: 0.5 – 3%
Hydrogen: 1 – 10%
Carbon monoxide: 0.1%
Oxygen: 0.1%
Hydrogen sulfide: traces.
7. Which of the following is needed for the formation of biogas from cow-dung and which not?
Water, Oxygen.
Answer
→ Water is required in the formation of biogas from cow-dung. And biogas is produced in the absence of oxygen in a closed system.
8. Name the clean fuel which can be obtained from cow-dung.
Answer
→ Biogas is the cleanest fuel that can be obtained from cow-dung. It typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen.
9. Apart from cattle dung, what other substances can be added to a biogas plant?
Answer
→ Apart from cattle dung, human excreta, agriculture wastes, vegetable wastes, poultry droppings, paper scrap etc. can also be added to a biogas plant. A biogas plant is an anaerobic digester that produces biogas.
10. Name any three forms of energy which could be harnessed from the sea.
Answer
→ The three forms of energy are:
(i) Tidal energy
It is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity.
(ii) Wave energy
It describes the process by which wind is used to generate electricity.
(iii) Ocean thermal energy
It is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters.
11. Write two forms in which solar energy manifests itself in sea.
Answer
→ Sea-waves energy and Ocean thermal energy manifests itself in sea.
12. Write the full form of OTE.
Answer
→ OTE stands for Ocean Thermal Energy. Ocean thermal energy is derived from the solar energy that is absorbed by the oceans.
13. What is the function of anaerobic micro-organisms such as anaerobic bacteria in a biogas plant?
Answer
→ Anaerobic bacteria help in the degradation of cow-dung in the presence of water but in the absence of oxygen and hence produces biogas. The most of the important bacteria involved in biogas production process are anaerobes.
14. State whether the following statement is true or false:
Tidal energy is one of the forms in which solar energy manifests itself in oceans.
Answer
→ False- Sea-waves energy and Ocean thermal energy are the forms of energy which solar energy manifests itself in oceans.
15. Fill in the following blanks with suitable words:
(a) Biomass is another form in which .......... energy manifests itself.
(b) Tidal waves build up and recede .............. a day.
Answer
→ (a) solar (b) twice
Short Answer Type Questions-Pg-148
16A. What is biomass? Give three examples of biomass.
Answer
→ Biomass is fuel that is developed from organic materials, a renewable and sustainable source of energy used to create electricity or other forms of power. Examples of biomass include landfill gas, wood, crops, garbage and alcohol fuels.
16B. Name the biomass which is still widely used as a source of heat energy in many households of country.
Answer
→ Wood is still widely used as a source of heat energy in many households of country.
17. What are the two ways in which cow-dung can be used as a fuel? Which of them is better and why?
Answer
→ Two ways in which cow-dung can be used as a fuel are:
a) In the form of cow-dung cakes, which can be used directly as a fuel.
b) By preparing biogas from cow-dung.
18. How is charcoal prepared? Explain why, charcoal is a better fuel than wood.
Answer
→ Charcoal is a lightweight, black residue, consisting of carbon and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow process-the heating of wood in the absence of oxygen.
Charcoal is better fuel than wood because: When the same amount of charcoal and wood are burnt, charcoal produces almost twice the heat produced by wood. Charcoal produces much less smoke than wood. Charcoal is a compact fuel that is more convenient to handle than wood.
19.Compare and contrast biomass and hydroelectricity as sources of energy.
Answer
→ Bio-mass is renewable sources of energy. It mass is derived from dead plants and animal wastes. Therefore it is naturally replenished. Wood, gobar gas etc. are some of the examples of bio-mass.
Hydro-electricity is also renewable sources of energy. But it is obtained from the potential energy stored in water at a height. Energy from it can be produced again and again.
20. Why biogas is considered an ideal fuel for domestic use?
Answer
→ Biogas is considered as an ideal fuel due to the following reasons:
a) It has an appropriate calorific value.
b) It is easy to store, handle and transport.
c) It is easily processed from cow dung and other waste materials.
d) It has also an appropriate ignition temperature.
e) It is also environment friendly and don't cause much harm to the environment.
f) It burns smoothly and does not leave behind much residue. Infact it contains negligible non-volatile material.
21A. Explain how tidal energy can be used to generate electricity.
Answer
→ During high tide, when the level of water in the sea is high, sea-water flows into the reservoir of the barrage and turns the turbines. The turbines then turn the generator and the electricity is produced. And during the low tide, when the level of sea-water is low, the sea-water stored in the barrage reservoir is allowed to flow out into the sea. This flowing water also turns the turbines and generates electricity.
21B. Why is tidal energy not likely to be a potential source of energy?
Answer
→ The tidal energy is not likely to be a potential source of energy because:
(i) The rise and fall of sea-water during high and low tide is not so high to generate electricity on a large-scale.
(ii) There are very few sites in the sea around the world that are suitable to build dams.(iii) Start up cost to build a tidal energy plant is high.
22. State two ways in which the energy of sea-waves can be harnessed.
Answer
→ Sea-waves energy can be harnessed by the following ways:
a) By setting up floating generators in the sea. They would move up and down with the sea-waves and their movement would drive the generators to generate electricity.
b) By letting the sea-waves move up and down inside large tubes so that when the waves move up, the air in the tubes is compressed and this compressed air can then be used to turn a turbine of a generator to produce electricity.
23. What is meant by ocean thermal energy? Explain how ocean thermal energy can be used to generate electricity.
Answer
→ The energy present due to the difference in the temperature of water at the upper surface and the deeper layers of ocean is known as ocean thermal energy.
Ocean thermal energy is used to produce electricity in an Ocean Thermal Energy Conversion power plant. A temperature difference of 20°C or more between the surface water and deeper water is needed for the working of these plants. The warm surface water of ocean is used to boil a liquid like ammonia or chlorofluorocarbon. The high pressure of liquid vapors is used to turn the turbine of a generator and produce electricity.
24. What are the limitations of energy that can be harnessed from the sea ?
Answer
→ There are certain limitations to harness energy from the sea. Those limitations are
a) High dams are required to be built to convert tidal energy into electricity which incurs lot of cost.
b) Very strong waves are required, which are not possible all the time.
c) Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.
d) To harness ocean thermal energy the difference in the temperature of surface hot water and the cold water at depth must be 20°C or more.
25. Suggest a safe and efficient method for the disposal of bio wastes and sewage materials. How is this method advantageous to us?
Answer
→ Biogas is a safe and efficient method for the disposal of bio wastes and sewage materials. In a biogas plant all the organic wastes such as cow dunk, plant wastes or the residue of any crop is used as a fuel for the production of biogas. Other waste products such as kitchen waste is also used. Hence, all waste is being disposed and converted into biogas.
26. Which of the following sources of energy are not derived from the sun?
Biomass, Wind, Ocean thermal energy, Geothermal energy, Nuclear fuels, Hydroelectricity, Wave energy, Coal, Petroleum, Tidal energy.
Answer
→ Following sources of energy are not derived from the sun:
● Geothermal energy-The heat present within the Earth.
● Nuclear fuels-The energy related to radioactive material.
● Tidal energy-The energy generated using the potential energy of water.
Long Answer Type Questions-Pg-149
27A. What is biogas? Name the major component of biogas.
Answer
→ Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Methane is the major component of biogas constituting about 60%.
27B. What are the raw materials used for making biogas?
Answer
→ Biogas is produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.
27C. Describe the construction and working of a biogas plant with the help of a labelled diagram.
Answer
→ Manure and dung are also fed into the biogas plant. In the fermenter, heated to approx. 38-40 °C, the substrate is decomposed by the micro-organisms under exclusion of light and oxygen. The final product of this fermentation process is biogas with methane as the main ingredient.
27D. Write any two uses of biogas.
Answer
→ Uses of biogas:
• It can be used for any heating purpose, such as cooking.
• It can also be used in a gas engine to convert the energy in the gas into electricity and heat.
27E. Write any two advantages of using biogas.
Answer
→ Advantages and Benefits of Biogas:
• Provides a non-polluting and renewable source of energy.
• Efficient way of energy conversion (saves fuel wood ).
• Provides a source for decentralized power generation.
28A. What is geothermal energy?
Answer
→ Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
28B. What is the source of heat contained in geothermal energy?
Answer
→ Hot rocks present inside the earth are the source of heat contained in geothermal energy.
28C. Explain how, geothermal energy is used to generate electricity.
Answer
→ Extremely hot rocks present below the surface of earth heat the underground water converting it into steam. When more and more steam is formed between the rocks, it gets compressed to high pressures. This high pressure steam is brought up through pipes and is used to run the turbine of a generator to produce electricity.
28D. State two advantages of geothermal energy.
Answer
→ Advantages of geothermal energy
i. It is a renewable source of energy.
ii. By far, it is non-polluting and environment friendly.
iii. There is no wastage or generation of by-products.
28E. State two disadvantages of geothermal energy.
Answer
→ Disadvantage of geothermal energy:
i. Only few sites have the potential of Geothermal Energy.
ii. Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.
iii. Total generation potential of this source is too small.
Multiple Choice Questions (MCQs)-Pg-149
29. Which of the following is not an example of a biomass energy source?
A. wood
B. biogas
C. atomic energy
D. cow-dung
Answer
→ It is a energy carried by atoms.
30. Most of the sources of energy that we use represent stored solar energy. Which of the following is not ultimately derived from the sun's energy?
A. wind energy
B. geothermal energy
C. fossil fuels
D. biomass
Answer
→ It is the energy present inside the earth.
31. The constituent of biogas which makes it an excellent fuel is :
A. butane
B. methane
C. propane
D. ethane
Answer
→ Biogas constitutes methane gas about 60% within it.
32. The major component of biogas is :
A. hydrogen
B. butane
C. hydrogensulphide
D. methane
Answer
→ Biogas contains around 60% of the methane.
33. Which of the following is more environment friendly ?
A. burning of diesel
B. burning of coal
C. burning of charcoal
D. burning of wood
Answer
→ It is a smokeless fuel with high calorific value.
34. Which one of the following is not renewable energy technology?
A. solar cells
B. windmills
C. nuclear power
D. tidal power
Answer
→ Nuclear powerplants usually use a very rare type of uranium, U-235 as a fuel hence categorizing it as a non-renewable source.
35. The rise of sea-water during high tide is caused by the gravitational pull of the:
A. Sun
B. Earth
C. Moon
D. Mars
Answer
→ It is caused by the attractive forces of the Moon and Sun’s gravitational fields as well as the centrifugal force due to the Earth’s spin.
36. One of the following is not required in the formation of biogas in a biogas plant. This is:
A. cow-dung
B. water
C. oxygen
D. anaerobic bacteria
Answer
→ As biogas can be prepared only in the absence of oxygen.
37. The fuel which is not obtained from biomass is:
A. firewood
B. cow-dung cakes
C. coke
D. charcoal
Answer
→ Coke is derived from destructive distillation of low-ash, low-sulfur bituminous coal.
38. The non-renewable source of energy among the following is :
A. hydroelectricity
B. sewage gas
C. natural gas
D. gobar gas
Answer
→ Natural gas is a fossil fuel which is a non-renewable source.
39. Geothermal energy is produced by the:
A. fission of radioactive materials
B. burning of coal inside the coal mines
C. combustion of natural gas deep inside the earth
D. fusion of radioactive substances
Answer
→ Geothermal energy is heat energy generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials.
40. The harnessing of which of the following leads to the destruction of large eco-systems?
A. thermal power
B. tidal power
C. hydro power
D. geothermal power
Answer
→ Construction of dams require a large amount of area.
41. Which of the following is not a consequence of establishing hydroelectric power plants ?
A. displacement of people
B. production of methane
C. occurrence of floods
D. ecological disturbance
Answer
→ The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants.
Questions Based on High Order Thinking Skills (HOTS)-Pg-150
42. A certain form of energy is available due to the difference in the temperature of water at the surface of the ocean and its deeper levels.
(a) Name the form of energy.
(b) Is this energy ultimately derived from the sun or not?
(c) Explain how this form of energy can be converted into electricity.
(d) What is the minimum temperature difference in water at the surface of ocean and its deeper level which is required to operate power plants based on this energy ?
Answer
→ (a) Ocean thermal energy is the energy generated due to the difference in the temperature of water at the surface of the ocean and its deeper levels.
(b)No this Energy isn't derived from the sun.
(c) Ocean thermal energy is used to generate electricity in an Ocean Thermal Energy Conversion power plant also called as OTEC power plant. A temperature difference of 20°C or more between the surface water and deeper water is needed for the operation of these plants. The warm surface water of ocean is used to boil a liquid like ammonia or chlorofluorocarbon. The high pressure of the vapors of liquid is used to turn the turbine of a generator and produce electricity.
(d)20°C is the minimum temperature difference in water at the surface of ocean and its deeper level which is required to operate power plants based on this energy.
43. The gravitational pull of the moon causes the sea-water to rise periodically.
(a) What name is given to the condition of the sea when its water is raised?
(b) What name is given to the condition of the sea when its raised water recedes?
(c) What name is given to the energy which can be harnessed from this natural phenomenon?
(d) Draw labelled diagram to show how this energy can be harnessed to generate electricity.
Answer
→ (a) The condition when the sea water rises is termed as high tide.
(b)When the rised water of the sea resides, the situation is termed as low tide.
(c)Tidal Energy (Tidal energy is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity)
(d)At high tide, water flows from sea into reservoir and turns the turbine.
At low tide, stored water flows out from reservoir into sea and turns the turbine.
44. When the material A mined from the earth ,is heated strongly in an insufficeint supply of air, it produces a solid fuel B which consists mainly of carbon. When another material C obtained from trees is heated in an insufficient supply of air, it produces another solid fuel D which also consists mainly of carbon. Name A, B, C and D.
Answer
→ A is coal; It is mainly made up of 65-95% carbon and also contains hydrogen, sulphur, oxygen and nitrogen.
B is coke; Coke is a fuel with few impurities and a high carbon content, usually made from coal.
C is wood;
D is charcoal; Charcoal is a lightweight, black residue, consisting of carbon and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances.
45. A certain form of energy which is not sourced directly or indirectly from the sun and does not cause any pollution is very easily converted into electricity. This form of energy is, however, not available everywhere. Moreover, it is technically very difficult and expensive to obtain it. Name the form of energy.
Answer
→ Geothermal Energy is the form of energy which is not sourced directly or indirectly from the sun.