An incandescent lightbulb uses 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. Everyday incandescent light bulbs 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.