From Engineering on December 20, 2007 in Electrical
In seven years, probably much sooner, not a single conventional bulb will remain in your home. The “normal” incandescent bulb invented by Edison 125 years ago was a groundbreaking step up from candlelight, but is inefficient for todays higher energy standards. Already phased out of production in Australia and Ireland, incandescents dont meet new U.S. standards imposed by the recent energy bill, which requires light to use 25 to 30 percent less energy by 2012.
But what is an incandescent bulb, and how does it work in comparison to the two big alternatives: CFLs and LEDs?
Incandescent bulbs light up when electricity runs through the filament, making it glow, or incandesce, with heat. Incandescent bulbs are inefficient because they give off 90 percent of their energy in wasted heat and only 10 percent in the form of visible light. The bulb itself becomes useless in a short amount of time, when the thin filament eventually evaporates along one area and breaks.
In contrast to incandescent bulbs that typically last 750-1000 hours, light emitting diodes (LEDs) last about 12 years. This is because LEDs dont require a filament, but release light through diodes, the simplest form of the semiconductor. When electrons move across the diode, they release photons expressed as light. The LED bulb then transfers that light outward.
Compact fluorescent lights, or CFLs, are another alternative, lasting 10 times longer than incandescents and saving 2000 times their weight in greenhouse gases. At about $2 each, they cost more than incandescent bulbs that cost about .50. CFLs and LEDs arent hot to the touch like incandescents because most of their energy is turned into light instead of heat. CFLs light up when electricity flows across an electronic or magnetic ballast located in a tube, making the gas in the tube glow with ultraviolet light. A white phosphor coating along the surface of the tube then emits a visible light.
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