The incandescent
lamp
is a device which produces light when an electric current is passed through a metal filament, heating the filament to a high temperature.
The first filament lamp, produced in 1878 by Joseph Swan in England, was a carbon linear filament lamp. See more
Typical theater Incandescent lamp.
The swan Carbon Filament lamp, 1878.
In 1880 Thomas A. Edison passed an electric current through thin filaments of carbonized threads that were tightly sealed inside a glass bulb from which all air had been removed by vacuum pumps. The
voltage
was then steadily increased until the white heat (incandescence) reached a stable, bright glow; the electric current kept the filaments glowing for 40 hours. Carbon filaments were later replaced by tungsten filaments, developed only in 1909 and becoming available in 1912.
All incandescent tungsten lamps have three basic parts:
A tungsten wire filament
A sealed glass bulb containing an inert gas or a vacuum to protect the filament from oxidation.
A base which provides mechanical support and enables the electrical circuit to enter the bulb.
