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Incandescent Light Bulb Filament
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The standard incandescent lamp is made up of
a small length of Tungsten alloy wire. It is
coiled up to conserve space. The filament is
heated by passing a DC current through the wire
where it reaches white hot temperatures. The filament
is generally protected from oxidation by air by using a glass
bulb filled with an inert gas. These are inefficient
but cheap devices, converting ~ 5% of the energy
they consume into light, the rest is waste heat. You can
see the effect of this heat on the filament itself as it
is becoming faceted due to an annealing of the metallic
structure. Today incandescent lamps
they are being replaced by LED's and CFL's.
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