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SCIENCE SOURCES OF ENERGY {SAMPLE QUESTION AND ANSWER} 1 . Which of following is more environment friendly? Burning of coal (b) burning of fire wood (c) burning of charcoal (d) Burning of diesel. 2. Major problem in harnessing nuclear energy is to split heavy nucleus (b) sustain nuclear reactions (c) Convert nuclear energy into electricity (d) dispose off nuclear waste. 3. Fusion reaction is also known as chemical reaction (b) elastic scattering (c) thermonuclear reaction (d) photo nuclear reaction 4. India exploded her first under ground nuclear device at Ranchi (b) Kota (c) Jaipur d) Pokhran 5.

Although charcoal is a clean and deter source of heat energy yet it cannot be used as a domestic fuel because it cause environmental pollution (b) produce less heat energy (c) cannot be stored easily (d) is expensive fuel 6. Write two advantages of using solar cooker? 7. Suggest two ways to reduce energy consumption? 8. What is geothermal energy? Write its advantages? 9. Why are many thermal power plants set up near coal or oil fields? (2) 10. Name three forms in which energy from ocean is made available for use. What are OTEC power plants?

How do they operate? (3) 11. List three forms of energy we use when we wake up from morning till we reach the school. Also from where we get these different forms of energy? (3) 12. Compare and contrast bio- mass and hydro-electricity as source of energy. The production cost of hydroelectricity is cheaper than the electricity produced in a thermal power station. Explain why? 13. What kind of mirror concave, convex or plane would be best suited for the use in a solar cooker. Why? What is the role of glass sheet used in a solar cooker?

Also write two disadvantages of using a solar cooker? 14. (i) What is biogas? Name two main combustible components of biogas? What is the use of spent slurry in a biogas plant? (iii) Name the microorganisms responsible for the fermentation of slurry in the digester? ANSWERS 6. (i) Pollution free Nutrition value of food is preserved when food is cooked inside a solar cooker. 7. (i) Fuels used for burning must be extinguished as soon as their use is over. (it) Bulb, fans and other electrical appliances must be switched off as you leave your room. . The heat energy obtained from hot rocks present in earth’s crust of geo thermal energy. The advantages of geo thermal energy are- i) Environment friendly. (it) Cost of converting geo-thermal energy into electricity is less. 9. The thermal power plants are usually set up near coal or oil fields so that the fuel is easily available and the problem of air pollution while transporting the fuel may be minimized. 10. (i) Muscular energy to perform different activities like taking bath, climbing stairs and muscular energy comes from food we eat. it) Fossil fuel energy used in bus or car to reach the school and this energy come from fossil fuels like petrol, diesel and CNG. (iii) Chemical energy in the form of breakfast and it lso comes from the food we eat. 11. (i) Tidal energy (it) Ocean waves energy (iii) Ocean thermal energy OTEC power plants are ocean thermal energy conversion plants. For operating OTEC temperature difference of 200C or more between the surface water of ocean and inside water of ocean is required to boil liquid like ammonia or chlorofluorocarbon (CFC).

The vapors of the liquid at high pressure used to rotate the turbine of the generator to produce electricity. 12. BIOMASS HYDROELECTRICITY 1 . Energy supplied by the burning of biomass causes pollution. 2. Energy can obtained by burning it directly or by a gobar gas plant. . lt does not cause any pollution. 2. Hydroelaectricity can be obtained by constructing dams. In a thermal power station coal is burnt to produce electricity where as hydroelectricity is produced by allowing the water to fall on turbines.

Water in rivers is available free of cost but the cost of extracting and transporting coal is very high. 13. Concave mirror will be best suited for the use in solar cooker because it concentrates all the sunlight to a point after reflection from the mirror and thus raises the temperature of that point. Plane glass plate does not allow the infrared or eat radiation entered in the box to go outside the box thus heating the box and creating green house effect. The two disadvantages of using a solar cooker are (i) Food cannot be cooked at night and on a cloudy day by using a solar cooker. it) Food cannot be cooked quickly by using a solar cooker. 14. (i) Biogas is a mixture of various gases formed when the animal dung mixed with water is allowed to decompose in the absence of air. The two combustible component of biogas are CH4 and H2 gas. (it) The spent slurry in biogas plant is rich in nitrogen and phosphorous required for the growth of plants and hence can be used as a manure. iii) Anaerobic micro- organism. 1 . A solar cooker may not cook food if. (1) (a) Interior of the box and the container of food are perfectly shining. b) Glass sheet over the box is not closed. (c) Solar cooker is placed in the shade. (d) All the above. 2. Radiations which are harmful to the living organisms are (1) (a) Infrared radiation. (b) ultraviolet radiations (c) Visible radiation. (d) micro waves 3. Solar cells are made of (1) (a) metals (b) insulator (c)semi conductors (d) none of these 4. The main constituent of CNG is (1) (a) butane (b) methane (c) ethane (d) propane 5. Which of the following is not a bio mass energy source? (1) (a) gobar gas (b) coal (c) wood (d) nuclear energy 6.

Hydro power is a renewable source of energy. Justify. (2) 7. Write two qualities of an ideal source of energy? (2) 8. What are the advantages of nuclear energy? (2) 9. Name two activities in our daily life in which solar energy is used? (2) 10. (a) Distinguish between renewable and non- renewable sources of energy? (b) Choose the renewable source of energy from the following list: coal, biogas, sun, natural gas. 1 1 . (a) name the device used to convert (i) Solar energy in to heat and it) solar energy in to electricity. (b) explain the working of windmill (3) 12. What is biogas?

How can biogas be obtained? Why is the use of biogas obtained from cow dung advised in preference to burning of cow dung cakes? (3) 13. What are the limitations of extracting energy from (a) the wind (b) waves (c) tides (3) 14. A student constructed a box type solar cooker. He found that if did not work Efficiently. What could this be due to? Give any four possible mistakes in the solar construction and operation of the cooker what maximum temperature Can ordinarily be reached inside a solar cooker? . (d) All the above 2. (b) Ultraviolet 3. (a) Seine conductors 4. b) Methane 5. (d) Nuclear energy 6. Hydro power is a renewable source of energy because if is derived from the renewable source of energy i. e. Sun. 7. The tow qualities of an ideal source if energy are- (i) It does not cause environ mental pollution- (it) Economical. 8. Advantages of nuclear energy- (i) A small quantity of fuel provides large amount of energy. (it) The nuclear fuel once inserted in nuclear power plant gives large amount of energy for a longer period of time. 9. (i) For cooking food using solar cookers. For drying clothes and food grains. 10. a) Difference between renewable and non-renewable sources : Renewable Sources Non-Renewable Sources The sources of energy which can never be finished and are continuously supplied by nature are known as renewable sources of energy. The sources of energy which are exhaustible (can be finished) and took lots of time to be formed again are known as non-renewable sources of energy. For example : Wind, the Sun, Bio-Gas, Hydro-power etc For example : Coal, Natural Gas, Petroleum etc. (b) Biogas and the sun are renewable sources of energy 11 . (a) (i) Solar cooker it) Solar cell. b) When the wind blows with a minimum speed of 1 5km/hr, the kinetic energy of the wind is used to rotate the blades of wind mill. The rotation energy of the blades is used to rotate the armature of the generator and generator in turn produce electricity. 12. Biogas is a mixture of gases namely methane, C02, H2 and H2S. it is obtained from an aerobic decomposition of cow dung and plants and animal wastes in a biogas plants. Biogas is advised for burning in preference to burning of cow- dung cakes because: (i) it cause no air pollution (it) It is a cheaper source of energy. 13. ) Wind energy is not sufficient to operate heavy machines and moreover it is limited to a certain place. (b) Energy of the waves can be extracted only if strong wind blows all the time across the sea. (c) Tidal power plant can extract the tidal energy from the water levels of high tide and low tide is very large. 14. He might have committed some mistakes. (i) Interior of the solar cooker not painted in black colour. (it) Instead of glass sheet, plastic sheet is used to cover it. (iii) Solar cooker is without insulation. (iv) Black containers have not been used. Maximum temperature is 1400C in solar cooker.