The incandescent lamp filament is very small, which is about 1/10~1/20 of the electric wire. The filament is winded into double helical filament, the pitch between wire is small, which is easy to concentrate heat, so the heat is generated by the current through the filament, the tungsten filament temperature is quickly reached above 2500 degrees, and keep the temperature of filament in the incandescent filament to emit white light.

Although the filament will make the power consumption be converted into heat, in order to maintain the tungsten filament for the incandescent, only 7%~8% energy of electrical incandescent filament will convert into light, but the light is visible light, which is many times stronger than electric wire.