house lighting dimmer switch question..

[crab bait]

here's an electrical question take i can't find an answer to..<br /><br />a modern type/now days dimmer.. if you set it to half dim,,say ( 100 w bulb now at 50 % ),, are ya still using a 100 watts worth of power .. or just 50 watts..??<br /><br />i know an amp-meter would tell me.. but it's a hassle..

 

[Paul Moir]

Re: house lighting dimmer switch question..

You're not using 100 watts (the dimmer doesn't waste 50w, or it would get blazing hot), but you're not using 50 watts either. <br />That is to say, if you run a 100w lightbulb with 50w of power, it'll be dimmer than a 50w bulb running at full power. Not much dimmer, but definitely dimmer. <br /><br />The cooler (and redder) a light bulb's filiment is running, the less efficient at producing light vs heat it is. Like those damn 60w candalabra bulbs that get hot enough to give you 3rd degree burns but don't provide much light.<br />The opposite would be halogen lights, which burn their filiments much hotter than a regular bulb. Which is why they're more efficient/brighter for a given wattage. <br /><br />Arn't you glad you asked?? <br /><br />(You ever notice the 25w, 40w and 60w candalabra bulbs make all about the same light? Or is it just me?)

 

[Mark42]

Re: house lighting dimmer switch question..

If you have some powerfull wattage on a dimmer, you can see the difference from full bright to dim by watching and counting the RPM of your meter. I have 8 75W recessed lights in the kitchen. Full power makes the meter spin! Cut them back and the meter slows down.<br /><br />We typically burn them just below full power. Those bulbs are $6 each and last a few years because of the dimmer.

 

[rogerwa]

Re: house lighting dimmer switch question..

If I am not mistaken, the dimmer clips the peaks of the sine wave so the peak to peak deflection is diminished.<br /><br />It doesn't change the frequency (60hz) nor does it change the amplitude. It simply clips off the top of the wave. If it changed the amplitude, it would be a lot dimmer as the bulb would only have the peak voltage for very little of the wave cycle. The sine wave while clipped looks a lot like a square wave..

 

[CalicoKid]

Re: house lighting dimmer switch question..

Electronic dimmers actually switch power on and off at different rates, they're roughly 95% efficient. That is a 100w lamp and dimmer at 50% power is consuming around 52.5watts.<br /><br />The old rotary solid state dimmers are resistive and less efficient but still save power.<br /><br />A lamp dimmed 10% (barely perceptable) will generally last twice as long as undimmed.

 

[crab bait]

Re: house lighting dimmer switch question..

THANKS ALL..<br /><br /> yeah,, my sister asked me this.. an i could't give/did not know the answer..<br /><br />i'll still give her a BS answer,tho.. ..

 

[levittownnick]

Re: house lighting dimmer switch question..

Paul Moir gave an excellent answer. Note that for maximum $ efficency you would not dim the lamps, instead use a wattage that gives the desired light. That doesn't allow for varing conditions so you may be willing to use more electricity per unit of light and have the dimmer. It should be noted that watts is not a measure of light output, for example, a fluorescent light of much less wattage than an incandescent may produce as much light. Also of note is that a dimmer is not always friendly to lamp life. That is because they cause the filament to vibrate which is destructive to the filament. You may have noticed a noise comming from the lamp of a dimmed bulb. That is vibration.