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Originally posted by james t kirk
Actually, you are all wrong.
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No, they're not.
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A dimmer switch does not work by varying the voltage. (TRUST ME, I have been zapped changing a fixture on a dimmer switch when the light looked like it was off. (It really wasn't off, just turned down so low, the bulb wasn't glowing.))
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That's because you pulled an electrical stupid. You need to understand switches more before you make assumptions like that. A switch only interrupts one leg of the circuit. That means the other leg is still ready to deliver power at the light. When you changed the fixture and touched that active leg, you got zapped because YOU provided a closed circuit with the ground. This is why we tell people to turn the power off at the breaker, not the switch, when they work on a light - the breaker kills BOTH legs.
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Dimmer switches work by turning the power on and off really quickly. As you know, AC power in North America operates at 60 hertz (or cycles per second). A dimmer switch works by turning the light on for a variable duration during each cycle.
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Half a point for effort. You're right in that NEW dimmers work like this. OLD dimmers worked with a variable resistor that did indeed lower the voltage.
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Dimmers are very very efficient with perhaps a 1% loss only in efficiency.
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The good ones have around a 2% loss. Cheap ones have more.
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Don't believe me, turn the dimmer knob right down till the light bulb isn't even glowing. Put the black wire in your left hand and the white wire in your right hand.
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Argh! Please learn something about how circuits work before you try to get TFP members killed! They could turn the switch OFF entirely and still get zapped. And if the current travels from their right hand out their left leg they could get seriously injured, especially if they're hot and sweating, standing on a metal ladder, etc. If you don't have GOOD experience with electricity ("duh, i done got shocked once" is NOT good experience) then don't run around telling people what to do with it. Some people are just dumb enough to believe anything they read on the internet and might actually try it.