GIST OF THE LESSON
1. A good source of energy is one that is able to provide large amount of work per unit volume or mass, be easily accessible at economical rate and can be easily stored and transported.
2. Conventional sources of energy: Fossil fuels, coal, petroleum, natural gas (thermal power plants), energy of flowing water (hydrowater plants), biomass, cow-dung, plants and vegetable wastes (bio-gas plants), wind energy (windmill).
3. Fossil fuels: Any naturally occurring organic fuel formed in the Earth’s crust, such as petroleum, coal and natural gas are called fossil fuels.
4. Alternate or non-conventional sources of energy: Solar energy-energy derived from sun, Nuclear energy-fission of radioactive substances, Geo-thermal energy-energy derived from hot spots under the earth, Ocean energy-ocean thermal energy, wave energy.
5. Non-renewal sources of energy: Fossil fuels like coal, petroleum and natural gas non-renewable.
6. Thermal power plants: Thermal power plants should be preferably located near coal or oil fields. It is easier to transport electricity than the fuel.
7. Hydropower plants: Convenient location to build dams. Potential energy of falling water is converted into electricity.
8. Biomass: The plant and animal products, which act as the source of fuel is said to be biomass.
9. Biogas: Cow-dung, various plants materials like the residue after harvesting the crops, vegetable waste and sewage decomposed in the absence of oxygen to give biogas (or Gober gas).
10 Biogas plants: Anaerobic micro-organisms (in the absence of oxygen) decompose complex compounds of cow-dung slurry or biomass-water mix produce biogas (60-80% methane).
11. Tidal energy: The gravitational pull of the moon on the rotating earth causes rise and fall in the level of water in the sea. The sea-level changes during the day. This phenomenon is called high and low tides and difference in sea levels gives us tidal energy. Tidal energy is harnessed by constructing a dam across narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity.
12. Windmill: The power of wind (>15km/h) gives rotatory motion of the windmill which is used to turn the turbine of the electric generator. The output of a single windmill is quite small and so a number of windmills are to be erected over a large area.
13. Nuclear reactor is a device in which a fission reaction is carried out in a controlled manner. The energy so released is used to heat water which then turns turbines and generates electricity. (Note: Fission of heavy radioactive isotopes gives tremendous amount of energy.)
14. Environment consequences: Sources of energy as are available produce lot of pollution in the atmosphere or cause environmental damage in other ways.
15. Quality of fuel is measured by its calorific value (heat regenerated by burning unit mass of a substance
16. Solar energy: 47% of the sun’s energy reaching the periphery of the earth’s atmosphere reaches the earth’s surface. One m2 of earth’s surface receives 1.4kJ/m2s. This is called solar constant. This energy is trapped by various means such as solar cookers, solar heaters and solar cells. A typical solar cell (using high quality silicon or silver) develops a voltage of 0.5-1V and can produce 0.7W of electricity. So a panel of solar cells is used.
Q.1. Name the largest component of biogas.
Ans. The largest component (upto75%) of biogas in methane.
Q.2. What is greenhouse effect?
Ans. The glass roof and glass walls of a greenhouse allow heat and sunlight to enter it but do not allow heat (infrared radiation) to escape. On account of this, greenhouse gets warmed.
Q.3. Name the gaseous fuel, out of the following which has the highest calorific value: Hydrogen, Methane, LPG, Biogas
Ans. Hydrogen.
Q.4.Why is CNG considered an environmental friendly fuel?
Ans. CNG does not produce toxic gases on burning.
Q.5. Name a fraction obtained during refining of petroleum which does not find use as a fuel.
Ans. Lubricating oil.
Q.6. Which of the following gases is a major constituent of biogas : Carbon monoxide, hydrogen, methane, carbon dioxide?
Ans. Methane (75%)
Q.7. What is slurry left over after generation of biogas in biogas plant used?
Ans. The slurry is rich in nitrogenous and phosphorus compounds and as such serves as an excellent manure.
Q.8. How is the increase in demand for energy affecting our environment adversely ?
Ans. We use fossil fuels to meet the increased energy demands. As a result of this, pollutants so produced adversely change the composition of the environment.
Q.9. Name the process by which energy is produced in a nuclear reactor.
Ans. In a nuclear reactor,energy is produced by the process of nuclear fission.
Q.10. Which one of the following is a renewable resource: Natural gas, petroleum, Ground water, Coal
Ans. Ground water.
MCQ on SOURCES OF ENERGY
Q.1. Choose the incorrect statement regarding wind power:
(a) It is expected to harness wind power to minimum in open space.
(b) The potential energy content of wind blowing at high altitudes is the source of wind power.
(c) Wind hitting at the blades of a windmill causes them to rotate. The rotation thus achieved can be utilized further
(d) One possible method of utilizing the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator.
Ans (b)
Q.2. Acid rain happens because:
(a) sun leads to heating of upper layer of atmosphere.
(b) burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere.
(c) electrical charges are produced due to friction amongst clouds.
(d) earth atmosphere contains acids.
Ans . (b)
Q.3. In a hydro power plant
(a)potential energy possessed by stored water is converted into electricity.
(b) kinetic energy possessed by stored water is converted into potential energy.
(c) electricity is extracted from water.
(d) water is converted into steam to produce electricity.
Ans. (a)
Q.4. which one of the following forms of energy leads to least environmental pollution in the process of its harnessing and utilization?
(a)nuclear energy (b) thermal energy (c) solar energy (d) geothermal energy
Ans. (c)
Q.5. Which of the following is a non-renewable source of energy?
(a)wood
(b)sun
(c)fossil fuels
(d) wind
Ans .(c)
Q.6. Ocean thermal energy is due to
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pressure difference at different levels in the ocean.
(d) tides arising out in the ocean.
Ans .(b)
Q.7. the major problem in harnessing nuclear energy is how to:
(a) split nuclei.
(b) sustain the reaction.
(c)dispose off spent fuel safely.
(d) convert nuclear energy into electrical energy.
Ans.(c)
Q.8. which is the ultimate source of energy?
(a) water
(b) sun
(c ) uranium
(d) fossil fuels
Ans. (b)
Q.9. The main constituent of biogas is
(a) methane
(b) carbon dioxide
(c) hydrogen
(d)hydrogen sulphide.
Ans.(a)
Q.10. the power generated in a windmill:
(a) is more in rainy season since damp air would mean more air mass hitting the blades.
(b) depends on the height of the tower.
(c) depends on wind velocity.
(d) can be increased by planting tall trees close to the tower.
Ans . (c)
Q.11. choose the correct statement:
(a)Sun can be taken as an inexhaustible source of energy.
(b) There is infinite storage of fossil fuel inside the earth.
(c) Hydro and wind energy plants are non polluting sources of energy.
(d) Waste from a nuclear power plant can be easily disposed off.
Ans.(a)
Q12. which part of the solar cooker is responsible for green house effect?
(a) coating with black colour inside the box
(b) mirror
(c) glass sheet.
(d) outer cover of the solar cooker
Ans.(c)
Q.13. In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because:
(a) its temperature increases. (b) larger amount of potential energy is converted into kinetic energy. (c) the electricity content water increases with height. (d) more water molecules dissociate into ions. Ans. (b).
Q.14. choose the incorrect statement:
(a) We are encouraged to plant more trees so as to ensure clean environment and also provide bio-mass fuel.
(b) Gober-gas is produced when crops,vegetable wastes etc.,decompose in the absence of oxygen.
(c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a lot of residual ash.
(d) Bio-mass is a renewable source of energy.
Ans.(c)
Q.15. Fuel used in thermal power plants is
(a) water (b) uranium (c) biomass (d) fossil fuels
Ans. (d)
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