In the mid 19th century, it still lights the candle or gas. Knowledge of electrical phenomena progr

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Keywords: bulb, tungsten filament incandescent light bulb, argon, krypton, melting, melting, rare gas, lamp, steam, thermal radiation, halogen lamp, CFL, energy-saving bulb, halogen bulb
Table of Contents Brief history filament electric lighting Interest tungsten Inside the bulb The role of rare gas halogen bulbs The future of this type of bulbs ... For more information about the different lighting
Tungsten is a metal, steel-gray color to white, the chemical symbol W and atomic number Z = 74. Can you explain the choice of the metal filaments for incandescent bulbs?
In the mid 19th century, it still lights the candle or gas. Knowledge of electrical phenomena progresses, but does not yet provide lighting application. The main difficulty in obtaining a stable filament is the fact that the presence of oxygen a filament heated to a high temperature burns instantly.
Sir Joseph Swan chemist (1828-1914, United sylvania synet7lp Kingdom) was the first to attempt to make a lamp. In 1860 he managed sylvania synet7lp to blush a piece of paper covered with carbon and maintained between two electrodes in an air vacuum bulb to prevent burning. But it encounters difficulties of evacuating the bulb and to provide electrical contact between the paper and the electrodes. In the 1870s, there are pumps capable of achieving an adequate quality of vacuum. In 1878, Swan gave a demonstration of the future electric light by wearing a wire to incandescence of carbon in a vacuum bulb.
The following year, in 1879, the great inventor Thomas Edison (1847-1931, USA), which has already imagined the phonograph and improved the microphone, as the challenge. It performs hundreds of tests, eg using a bamboo bent in U and connected to two platinum son. With a filament of carbonized cotton, it gets a lamp that illuminates for about 48 hours. Edison protects all his discoveries by patenting.
In 1883, after a legal dispute over the priority of inventions, Swan and Edison founded the Edison & Co. SWAN UNITED ELECTRIC LIGHT In 1909, the tungsten filament replaces the filament of carbon, which definitely improves the longevity of the lamps filament.
Today, the filament within the bulb is made of tungsten because it is the metal that has the highest melting point (3410 C by site-www.techniques ingenieur.fr 3422 C or according www.webelements.com). A tungsten filament can be heated to high temperature, remaining solid and rigid up to approximately 2700 K, without evaporating too quickly.
The radiation of a black body at T = 2900 K is maximum for the wavelength λ m = 1 micron (law of "displacement" of Wien: λ m T = 2898 μmK). Much of the radiation of incandescent tungsten filaments is always emitted in the infra-red radiation which heats without light.
Ideally, it would reach the temperature of 5800 K for reproducing a white spectrum, similar to that of sunlight and adapted to the spectral sensitivity of the eye. By increasing the temperature of the incandescent filament, it moves the radiation from the infrared to the visible sylvania synet7lp light and improves the efficiency of lighting.
If the ampoule was filled with air, the filament heated to a high temperature burn in the presence of oxygen, and the lifetime does not exceed the second. A solution is, as has been seen, evacuating the bulb. In these common lamps, tungsten sylvania synet7lp filament is evaporated little by little and is deposited on the walls i