How Electric Lighting Works

Electric lighting converts highly versatile electricity into usable light. Very different technologies can be employed to do this.

In incandescent lighting—the standard light bulb invented 130 years ago by Thomas Edison—electric current passes through a thin wire (filament) with high electric resistance. The heated filament glows, emitting a soft, high-quality light. Most incandescent lamps have a relatively short lifespan, ending when the filament breaks, cutting the electric circuit. Halogen lamps are a version of incandescents in which the filament is inside an inner tube that includes a halogen gas, such as iodine or bromine; this increases filament life and improves energy performance. Incandescent lamps convert as much as 90% of the electricity into heat, with only 10% delivered as visible light.