Electric Power
Electric power is generated by converting heat, light, chemical energy, or mechanical, energy to electrical energy. Most electrical energy is produced in large power stations by the conversion of mechanical energy or heat. The mechanical energy of falling water is used to drive turbine generators in hydroelectric stations, and the heat derived by burning coal, oil, or other fossil fuels is used to operate steam turbines , or internal-combustion engines that drive electric generators. Also, the heat from the fissioning of uranium or plutonium is used to generate steam for the turbine generator in a nuclear power plant.
Electricity generated by the conversion of light or chemical energy is used mainly for portable power sources. For example, a photoelectric cell converts the energy from light to electrical energy for operating the exposure meter in a camera, and a lead-acid battery converts chemical energy to electrical energy for starting an automobile engine.
Electric power produced in large power stations generally is transmitted by using an alternating current that reverses direction 25, 50, or 60 times per second. The basic unit for measuring electric power is the M watt - the rate at which work is being done in an electric circuit in which the current is one ampere and the electromotive force is one volt.
Ratings for power plants are expressed in kilowatts (1,000 watts) or megawatts (1 million watts). Electric energy consumption normally is given in kilowatt-hours - that is, the number of kilowatts used times the number of hours of use. Electricity is clean, inexpensive, and easily transmitted over long distances. Since the 1880's, electricity has had an ever-increasing role in improving the standard of living. It now is used to operate lights pumps, elevators, power tools, furnaces, refrigerators, air-conditioners, radios, television sets, industrial machinery, and many other kinds of equipment. It has been counted that in developed countries about 43°, of the electric power is generally used for industrial purposes, 32% in homes, and 21% in commercial enterprises.