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Explain renewable and nonrenewable sources of energy and mention the advantage of such classification.?ANS:
Those sources of energy which will be available as long as the heat from sun reaches the earth are called renewable sources of energy. The renewable sources are generally pollution-free.Solar energy, hydel energy, wind energy, tidal energy, etc. are renewable sources of energy.
Those sources of energy whose formation takes millions of years and which are limited in supply are called nonrenewable sources of energy.Nonrenewable sources create heavy pollution. Coal, petroleum, natural gas, etc. are nonrenewable sources of energy. The advantage of such classification of energy sources is that it helps us to decide about the conservation of available energy sources for future generation.
It also helps us in development of alternative sources of energy accelerating the scope for the development of appropriate technology
Write a note on solar cooker.
ANS:
Solar cooker is a device that uses solar energy in the form of heat for cooking food. As shown in figure, solar cooker consists of a container box whose body is made up of nonconducting plastic or fibrous material and insulated from outside to prevent heat loss.
A plane mirror is fixed on the top of the box in such a way that it reflects sun rays into the box. Solar cooker contains small containers painted black externally to absorb heat. The box is covered with a glass-sheet to retain the heat inside due to greenhouse effect. This he develops about 100-140°C temperature inside the box within 2-3 hours when placed in sun rays.
ADVANTAGES
1. There is no combustion of fuel.
2. Maintenance is negligible.
3. It is pollution-free.
4. The natural taste of the food is maintained as it conserves all nutrients.
5. During the preparation of food no personal attention is needed.
LIMITATIONS
1. Food cannot be cooked on a cloudy day or in absence of direct sunlight
2. It takes very long time for cooking.
Write a note on Solar Cells.?
ANS:
Solar cell is a device that converts solar energy directly into electrical energy. Earlier, it was observed that when solar rays fall on a thin wafer of selenium, electricity is generated. A solar cell made of selenium wafer converts only 0.7% of solar energy into electrical energy which is a very small output and hence impracticable for generating electricity.
This electricity is quite small and to get large amount of electricity several solarcells are connected together in series. This arrangement is called Solar Panel.
* ADVANTAGES:
1. Solar cells provide eco-friendly environment.
2. Solar cells can be used anywhere as a self-generating source of electricity.
* LIMITATIONS:
1. The availability of the special grade silicon required for making solar cells is very limited.
2. The cost of connecting material used in solar panels is very high as it is generally silver.
3. The current produced by solar cells is direct current (DC) and it has to be converted to alternating current (AC) for some devices. This involves high cost and loss of efficiency.
4. The conventional method of storing solar energy in storage batteries is not efficient enough.
* USES:
1. In artificial satellites.
2. In radio wireless transmission.
3. In TV transmission.
4. In traffic signals and research centres.
5. In calculators and watches.
6. In solar cars.
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