Incandescent Light (Encyclopedia of Science)
Incandescent light is given off when an object is heated until it glows. To emit white light, an object must be heated to at least 1,341°F (727°C). White-hot iron in a forge, red lava flowing down a volcano, and the red burners on an electric stove are all examples of incandescence. The most common example of incandescence is the white-hot filament in the light-bulb of an incandescent lamp.
History of incandescent lamps
In 1802, English chemist Humphry Davy (1778829) demonstrated that by running electricity through a thin strip of metal, that strip could be heated to temperatures high enough so they would give off light. The strip of metal, called a filament, is resistant to the electricity flowing through it (the thinner the metal, the higher the resistance). The resistance turns the electrical energy into heat, and when the filament becomes white-hot, it gives off light. It incandesces because of the heat. This is the basic principle by which all incandescent lamps work.
In the decades following Davy's demonstration, other scientists and inventors tried to develop workable incandescent lamps. But these lamps were delicate, unreliable, short-lived, and expensive to operate. The lifetime was short because the filaments used would burn up in air. To combat the short lifetime, early developers used thick, low-resistance filaments, but heating...
(The entire section is 1189 words.)
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