Electrical filament
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An electrical filament is a thread of metal, usually tungsten, which is used to convert electricity into heat and light for the incandescent light bulb as made in 1878 by Joseph Wilson Swan, among others. The first successful light bulb filaments were made of carbon (from bamboo), only later replaced with tungsten.
An electrical current travels through the filament and because of the electrical resistance of the filament makes it white-hot and generates light. It is normally in a vacuum or a noble gas or inert gas inside a glass enclosure to stop oxidation. Small amounts of a halogen can be added to facilitate transport of sputtered tungsten atoms back to the filament, resulting in significantly prolonged lifetime when used at higher temperatures, which is exploited in halogen lamps.
Electrical filaments are used in hot cathodes of various types of vacuum tubes and electron guns as sources of electrons.
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