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Q & A: Light Dimmers

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Most recent answer: 10/22/2007
Does using a light dimmer save energy, or does the dimmer just dissipate about the same amount in heat? Does it depend on the dimmer type?
- Roger Kaiser (age old)
U of I Alum, West Grove, PA
Roger -

Modern light dimmers are actually much more efficient than they used to be. Back in the "old days", they were basically just resistors that limited the current in a circuit. Since resistors dissipate power, this is a wasteful way to do it. Most modern dimmers use what are called Silicon Controlled Rectifiers (SCR's), which limit the power sent to lights by quickly switching on and off rather than by resistive loading.

Have a look at


(published on 10/22/2007)

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