filament (wire)

A filament is a length of tungsten resistance wire which glows white-hot on carrying a suitable electric current, used in incandescent filament lamps filled with inert gas or a vacuum. Lamp filaments, from 0.015 to 0.045 millimeter in thickness, are coiled once or twice (coiled coil) before being fused into the neck of the lamp.


Heater filaments in electron tube cathodes operate at only red heat.