Sources Of Energy

S.S.C SOURCES OF ENERGY

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S.S.C NOTES

Q. I. Define the following: 1. Solar cell: The device that converts incident solar energy into electrical energy is called solar cell. 2. Solar energy: The energy that is continuously emitted by the sun in the form of heat and light is called solar energy. 3. Bio – mass : The organic matter present in the bodies of living organisms is called biomass ( or ) the material contained in the bodies of plants and animals is called biomass. 4. Bio gas: The gaseous mixture obtained by the degradation of animal and plants wastes by anaerobic respiration of microorganisms in the presence of water is called biogas. 5. Solar Dryer: The device, which uses solar energy to dry agricultural products is called solar dryer. 6. Slurry: The mixture of animal dung with water, which is fed into the digester is called slurry. 7. Photo Voltaic Cell:- A device, which converts incident solar energy into electric energy is called Photovoltaic or solar cell. 8. Solar Panel: The panel on which many solar cells are suitably mounted is called solar panel. It is used for operating T.V. Sets, Water pumps and street lighting. 9. Fossil fuels: Fossil fuels are formed over millions of years by the burial of plants and animals. Fossil fuels are energy rich molecules of carbon compounds originally made by plants. Examples. Coal, petroleum and natural gas. 10. Charcoal. Charcoal is obtained by burning wood in an insufficient supply of air. Q II. Answer the following in briefly. 1. Describe solar water heater with neat and labeled diagram? Ans. A solar water heater consists of two parts_ i. An insulated storage tank. ii. A flat plate collector. The insulated storage water tank is connected to the flat plate collector with pipes. Cold water in the storage tank enters The flat plate collector which is exposed to solar energy, where it gets heated up. Once the water gets heated up it expands, and Become lighter and rises to the top of the storage tank. Its place is taken by the cold water from the bottom of the tank. Hot water from the top of the tank is thus available for use. Whenever hot water is withdrawn its place is taken by the cold water which enters the tank at its bottom. 2. Write about solar cooker with neat labeled diagram. Ans. A box type solar cooker consists of a Rectangular metallic, double walled box. Between the walls a thermally insulating material such as glass or wool is filled. The inner surface of the box is painted black as black surface absorbs 98% of the 5

S.S.C SOURCES OF ENERGY

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S.S.C NOTES

incident heat radiation. The outer surface of the vessels is also painted black. It has a glass cover at top. Food to be cooked is kept in shallow vessels, which are placed in the inner box. Sunlight is reflected on them using plane mirrors. Thus, food is cooked in shallow vessels with the help of reflected sunlight. 3. Write a short notes on_ i. Solar Dryer:1. The device, which uses solar energy to dry agricultural products is called solar dryer. 2. Solar Dryer is used for drying agricultural products. 3. If drying is done by spreading a product on open ground, the process is slow and the disadvantage is that dust and insects get mixed with the product. 4. In solar drying this is prevented and process of drying is quick. 5. Drying process removes moisture and helps in preservation of agricultural products. 6. Solar Drying is also used to prepare dry fruits. ii. Photo Voltaic Cell:1. The device, which converts incident solar energy into electrical energy is called photovoltaic or solar cell. 2. Solar cell is arranged in rows and columns and then suitably mounted on a panel. 3. It contains no moving parts hence needs any maintenance. 4. Solar cells works satisfactorily even in diffused radiation. 5. It is an eco – friendly device since it does not produce any pollution. iii. Solar distillation:- In many small villages brackish or saline water is available instead of fresh drinking water. Using solar energy brackish water can be converted into pure water by solar distillation. iv. Charcoal. 1. Charcoal is obtained by burning wood in an insufficient supply of air. 2. In this process the volatile material from wood is removed and charcoal is left behind. 3. It is a good solid fuel and mainly contains carbon. 4. It is better fuel than wood and burns without smoke. 4. Explain how solar energy is produced. Ans. 1. Interior of the sun in extremely hot and its temperature is about 2 x 107 0 C. 2. It mainly contains hydrogen gas. 3. At this extremely high temperature four hydrogen nuclei combine to forma helium nucleus by nuclear fusion. 4. However, the mass of helium nucleus is slightly less than the total mass of four hydrogen nuclei. 5. this difference in mass is converted into energy. Thus solar energy is produced. 5. What are the advantages of uses of solar energy. Ans. 1. Solar energy forms an extremely large and inexhaustible source of energy. 2. Solar energy is a clean source of energy and does not effect on environment. 6

S.S.C SOURCES OF ENERGY

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3. Solar energy is freely available in sufficient quantities in all parts of the earth inhabited by mankind. 6. What are the difficulties involved in the use of solar energy? Ans. The difficulties involved in the use of solar energy are_ 1. Solar energy is not a concentrated source of energy. 2. Due to rotation of the earth about its axis and its motion around the sun, the solar energy available at a given place is never constant. 3. Therefore, it is necessary to store solar energy for its technical application. 4. To obtain sufficient solar energy for technical application large collecting surfaces are required which are highly expensive. 5. Above all the storage equipment used for storing solar energy are also very costly. 7. Explain space heating and space cooling? Ans. Solar energy can be converted into electrical energy by solar panels. This electrical energy is used to operate heaters and coolers to provide warm living conditions in winter and cool living conditions in summer. 8. Explain how energy from flowing water is used to generate electrical energy. Ans. Flowing water is used to generate hydroelectric power. The water of a river is stored in a dam. It is then allowed to flow under gravity through the pipes. As it flows down its Potential energy converted into Kinetic energy. The water falls down in turbine wheels connected to electric generators, which generate electricity. 9. How is Ethanol prepared? Give its uses. Ans. Ethanol is prepared by the fermentation of the carbohydrates from food grains the crops like maize, sugarcane etc. Uses of Ethanol: 1. Ethanol is a good liquid fuel. 2. Ethanol mixed with petrol is an efficient alternative fuel for automotive engines. 10. What are the advantages of biogas? Ans. 1. It burns without smoke and produces large amount of heat. 2. It is used for domestic purposes and street light. 3. It is used for operating engines. 11. Describe biogas plant with neat and labeled diagram. Ans.

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S.S.C SOURCES OF ENERGY

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S.S.C NOTES

1. Biogas plant consists of a well called digester. 2. It is divided into two equal compartments by a vertical wall. 3. The partition wall helps to direct the flow of slurry. 4. The digester has two pipes connected at its bottom. 5. Mixture of animal wastes and water in the form of slurry is fed in the digester through one pipe where biogas is produced by anaerobic fermentation. 6. The biogas rises upwards and is collected in the dome, which floats on the slurry. 7. A valve connected to the dome is used as an outlet for the gas. 8. Sludge remaining in the digester is removed from the other pipe and can be used as a fertilizer.

III. Distinguish between 1. Solar energy 1. Solar energy is freely available on a large scale. 2. It is pollution free source of energy. 3. It is available every where on earth. 4. It is not a concentrated source of energy.

Fossil Fuels 1. Fossil fuels are not abundantly available.

Wood 1. Wood is one of the biomass. 2. It consists of many volatile compounds. 3. Wood produces 17 KJ/g of heat. 4. Combustion of wood produces smoke.

Charcoal 1. Charcoal is a conversion of wood. 2. It consists of mainly carbon. 3. It produces 33 KJ/ g of heat. 4. Combustion of Charcoal is almost smokeless.

2. Fossil fuels create pollution. 3. They are obtained at a particular place. 4. They are concentrated source of energy.

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