Electrical filament

An electrical filament is a thread of metal, usually tungsten, which is used to convert electricity into light in incandescent light bulbs (as developed in 1878 by Joseph Wilson Swan, among others), and into heat in vacuum tube devices.

Filament of a 200 watt incandescent lightbulb highly magnified

The first successful light bulb filaments were made of carbon (from bamboo), only later replaced with tungsten.

Explanation

An electrical current travels through the filament and because of the electrical resistance of the filament makes it white-hot and generates light and heat. 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 evaporated 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.

Types of Filament

There are several different types of filament configuration available and it all depends on the lamp itself, and what characteristics are required. Some of these include but are not limited to C-6, CC-6, C-2V, CC-2V, C-8, CC-88, C-2F, CC-2F, C-Bar, C-Bar-6, C-8I, C-2R, CC-2R, Axial.

External links

• An brief article explaing the light bulb - "The Composition of the Light Bulb"
• The history of the light bulb