Exploring Power Consumption of Dimmer Switches

In summary, a dimmer switch/knob/potentiometer used to control the lights in a house, for example, uses the same amount of power no matter if it is just barely on, or turned up all the way, so it really doesn't matter (energy usage wise), what the switch is turned to.
  • #1
mrjeffy321
Science Advisor
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I heard that a dimmer switch/knob/potentiometer used to control the lights in a house, for example, uses the same amount of power no matter if it is just barely on, or turned up all the way, so it really doesn't matter (energy usage wise), what the switch is turned to, it will use the same amount of energy?
I would think this is false, since power is volts * amps, and the voltage is pretty much constant, say "out of the wall" voltage of 110 volts, then amps is the only thing that would effect the power consumption.
Amps are calculated by volts over resistance, and we already assumed volts were constant, so ressitance is therefore the only thing effecting power consumption.
As you turn the dial on the potentiometer, the resistance increses or decreases, thus making the power consumption go up or down depending on a lower of higher resistance.

So is my conclusion correct, or the person who I heard this from, who claims to have gotten it from an elecrtician?
 
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  • #2
Total BS. A dimmer switch in a house is more than just a resistor inserted in series with the load. At one time there were dimmers like this however. I recall seeing a very old lamp that had a rotatable base on the socket which was a variable resistor. The thing ran VERY hot. What happens in a situation like that is all of the load current is also passing through the resistor and any time you pass current through a resistor energy is dissipated in the form of heat. Heat means waste unless you are trying to heat your house with it. The total current used with one of these in dim mode is still less than full current.

The modern dimmer switches are actually just that, switches. They allow the current to fully flow for a set amount of time in each AC cycle. Set to really dim and they will allow the current to flow for only the tail end of half of the cycle before the voltage crosses zero. When the voltage passes through zero the device that does the switching opens up and is not turned on until the same point in the next half of the cycle. These dimmers are essentialy pulse width modulators. They are either on or off but the perception is a dimmer.
 
  • #3
so it is like turning the light on an off very very quickly, not allowing it to get up to its full brightness at each cycle.
 
  • #4
Modern dimmer switches implement semiconductor-based hysteresis devices called thyristors (specifically TRIACs) which take advantage of break-over voltages much like neon-tubes and lightning bolts do.

Read about them:
http://www.allaboutcircuits.com/vol_3/chpt_7/6.html
 

Related to Exploring Power Consumption of Dimmer Switches

1. What is a dimmer switch and how does it work?

A dimmer switch is a device that allows you to adjust the intensity of a light bulb. It works by adjusting the amount of electrical current that flows to the bulb, thereby controlling the brightness of the light.

2. What factors affect the power consumption of dimmer switches?

The power consumption of dimmer switches can be affected by several factors, including the type of bulb being used, the amount of light being emitted, and the load rating of the dimmer switch itself.

3. Do dimmer switches save energy?

Yes, dimmer switches can save energy by allowing you to use less electricity for lighting when full brightness is not needed. However, the actual energy savings will depend on the type of bulb and how frequently the dimmer switch is used.

4. Can dimmer switches affect the lifespan of light bulbs?

Yes, dimmer switches can affect the lifespan of light bulbs. Using a dimmer switch at a lower brightness level can help extend the lifespan of bulbs, while using them at higher brightness levels can decrease their lifespan. It is important to use dimmer switches with compatible bulbs to avoid any negative effects.

5. Are there any safety concerns with using dimmer switches?

There are some safety concerns with using dimmer switches, such as the risk of electrical fires if the switch is not installed properly or if it is overloaded. It is important to follow manufacturer instructions and use dimmer switches that are rated for the specific load and type of bulb being used.

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