How does a light bulb work?
An incandescent light bulb, like the ones on your desk lamp, use heat caused by an electrical current. When electrical current passes through a wire, it causes the wire to heat. The wire, or filament, gets so hot that it glows and gives off light. Light bulbs for everyday usage have a filament made of tungsten. Since the hot tungsten would quickly burn away if it were exposed to oxygen, it must be placed in a sealed glass bulb, which is either evacuated or filled with a gas that won’t let it burn. Thomas Edison, the creator of the light bulb, thought that it would take him six weeks to develop it, but instead it took more than one year. Of this experience, he famously said, “I have not failed … I have just found 10,000 ways that will not work.” When he finally got it right, in 1879, it was due to two important factors: First he put the filament in a glass bulb and then he removed the air (including oxygen) from inside the bulb. Edison tested more than 1,500 materials to find the right filament, including coconut fibers, fishing line, and facial hair.