Light bulb

In an incandescent light bulb, an electric current passes through a filament, heating it to produce light. A glass enclosure prevents oxygen in the air from oxidizing and destroying the hot filament.

Thomas Edison was best known for his development of the light bulb because of the factors he helped to promote—a long-lasting filament, the use of a higher vacuum within the bulb than others were able to produce, and a power distribution system that would make the light bulb of practical value in buildings, streets, and communities. Edison’s carbonized filament of bamboo could emit light for more than 1,200 hours. Today, a filament made of tungsten wire is often used, and the bulb is filled with an inert gas such as argon to reduce evaporation of material from the filament. Coiled wires increase the efficiency.

Incandescent lights are inefficient because about 90% of the power consumed is converted to heat rather than visible light. Today, more efficient forms of light bulbs such as fluorescent lamps and LEDs are starting to replace them, with bulbs typically lasting up to 10 years.

Impact
The simple incandescent bulb once replaced inefficient and dangerous lamps and candles. It was one of the inventions that changed the world forever, and for what Edison was the most famous. Today we cannot imagine a world without which a simple flick of a switch can instantly transform our surroundings from darkness into illumination.