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How CFL Bulbs Work

The compact fluorescent light bulb stands poised to replace Edison's most famous invention as the icon of ideation. See more green science pictures.
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As the symbol of innovation, the incandescent light bulb is not very innovative. It hasn't changed much since Thomas Edison introduced it in 1879. Even today, it still generates light by heating a tungsten filament until it reaches 4,172 degrees Fahrenheit (2,300 degrees Celsius) and glows white-hot. Unfortunately, all of that white light is not very green. A good deal of electricity -- electricity from coal-fired powered plants responsible for spewing greenhouse gases into the atmosphere -- is required to make an incandescent bulb burn brightly. Only 10 percent of that juice goes toward making light. The rest is wasted as heat.

Luckily for our CO2-soaked planet, there's a new type of light bulb that stands poised to replace Edison's most famous invention as the icon of ideation. It's known as the compact fluorescent light bulb, or CFL, and its illumination comes by way of a much different mechanism. Instead of a glowing filament, CFLs contain argon and mercury vapor housed within a spiral-shaped tube. They also have an integrated ballast, which produces an electric current to pass through the vaporous mixture, exciting the gas molecules. In older CFLs, it took several seconds for the ballast to produce enough electricity to ramp up the excitation. Newer CFLs have more efficient ballasts and require a shorter warm-up. Either way, when the gas gets excited, it produces ultraviolet light. The ultraviolet light, in turn, stimulates a fluorescent coating painted on the inside of the tube. As this coating absorbs energy, it emits visible light.

Believe it or not, CFLs are the descendants of the lightsaber-shaped fluorescent bulbs that still flicker in garages and workshops all over the world. But these are not your father's fluorescents. Despite their heritage and their similarities to incandescent bulbs -- they both require electricity, they have a glass cover, they have a threaded base -- CFLs are emerging as the biggest thing in interior illumination since the candle.

This article will explain what all the fuss is about. It will examine the good, the bad and the ugly of CFLs so that you can use them with confidence. Let's start with the good -- the many benefits that come from using compact fluorescent bulbs.

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