How does a lightbulb work?

(Lansing State Journal, June 17, 1992)


Question submitted by: Haley Palazzolo

There are two types of lightbulbs: incandescent and fluorescent.

An incandescent bulb 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 wonít let it burn.

Another common type of light is the fluorescent lamp.  A fluorescent lamp is a glass tube filled with argon gas and a tough of mercury.  When electrical current is passed through the gas the atoms of the gas pick up energy and radiate it in the form of ultra-violet light (and some heat).  The UV light then strikes the inside of the tube, which is coated with a phosphor.  The phosphor glows, giving off the light we see.

Fluorescent lamps donít require high temperatures to produce light, like incandescent bulbs do.  Energy must be used in heating the incandescent bulb, and a large part of that energy is lost as heat, not light.  In the fluorescent lamp, a larger portion of the energy is radiated as light


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