In a solar heater, plane reflector the solar radiation is reflected into a blank pipe containing water. If the solar radiation falls on the plane reflector, on the black pipe it reflects the solar radiation. The black pipe absorbs the heat and uses it for heating water in it.
It consists of a large number of movable plane mirrors and a parabolic reflecting surface. The parallel beam of light falling on the parabolic mirror is focused at a small area, F
A solar furnace is used in melting metals of high melting point.
A device which converts sunlight into electrical energy is known as a solar cell.
The solar cell consists of an array of semiconductor device called diode. When solar energy falls on such a diode, a small potential difference is created across it. When the large numbers of diodes are connected in series, a large potential difference can be obtained. As the large numbers of series of diodes are connected in parallel, a large current can be obtained. Each diode is called solar cell and an array of such cells is called a solar battery or solar panel. For example, to run a water pump by the solar battery, the external battery is connected to run an electric motor.
The main advantages of solar cells are
Uses of Solar Cells
The material which produces energy while burning is called fuels. Petrol, wood, kerosene, diesel, etc are the examples of fuel.
The earth has three layers i.e., the core, the mantle and the crust. The core is the central part of the earth surrounded by the mantle. The outermost part of the earth which surrounds mantle is the crust. The mantle of the earth has molten mass called magma. This magma consists of molten rocks, gases and steam at very high temperature. Due to some geological changes, the hot magma rises up and is collected in the crust of the earth. The regions in the crust where the hot magma is collected are called hot spots. The heat energy stored in the hot spots of the earth’s crust is called geothermal energy.
The rise and fall of the ocean due to the attraction of the moon is called tide. The rise in water is called high tide and fall in water is called low tide. The kinetic energy of water during tides is used to produce electricity.
Tides power plants are constructed near Bays. Tides rising water is allowed to fall on the turbine of the generator which produces electricity. Thus, the kinetic energy of the water is converted into electrical energy.
During low tides, gates of the dam are closed and hence the water level behind the dam rises. The raised water has potential energy. Again gates are opened and the water is allowed to fall back into the bay. This falling water is used to rotate the turbine of the generator. Hence, the electricity is produced.
Manu Kumar Khatry, Manoj Kumar Thapa, Bhesha Raj Adhikari, Arjun Kumar Gautam, Parashu Ram Poudel.Principle of Physics. Kathmandu: Ayam publication PVT LTD, 2010.
S.K. Gautam, J.M. Pradhan. A text Book of Physics. Kathmandu: Surya Publication, 2003.
The regions in the crust where the hot magma is collected are called hot spots.
The heat energy stored in the hot spots of the earth’s crust is called geothermal energy.
The rise and fall of the ocean due to the attraction of the moon is called tide.
The rise in water is called high tide and fall in water is called low tide.
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