Light fixtures makes the lamp hot. Dimming is usually done by switching the light off and on again very fast making a pause where it draw no power, the longer the pause, the dimmer it gets. But that is with incancesgent bulbs where the bulb itself contain very little air next to the light filament. Air is slower to heat up and cool down but it does after a while. heating make it expand and cooling make it contract, so if there is air in your bulb the the noise you hear is probably the glass exterior of the bulb vibrating as it contract and expand to balance the air pressure. Such bulbs should NOT be called dimmable, but a lamp seller desperate for a sale might say they are anyway. It may be just the bulb that has a leak letting in air. so take the lamp back to the shop and tell them you want a different one because it makes noises when you dim it. Neon lights are never dimmable, LED bulbs may be, and incandescent bulbs always are.
The dimmer is an electrical device called a varistor, short for variable resistor. As you dim the bulb the resistance is increased in the dimmer, causing it to heat up. Sometimes certain devices will emit a 60Hz sound when current flows through them...for unknown reasons. It does mean it is probably faulty and needs to be replaced. I'll be over in a few. Easy fix. (Reference...20 years electronics tech in the Navy.)
Sometimes there is an incompatibility between the bulb and the dimmer switch. Like if it is an LED light the dimmer must be LED dimmer, as well as the light must be dimmable. Or if you put a bulb that is not dimmable on a dimmer, then when you dim it won't dim all the way down and you get a high pitched noise. Sounds like that's what you have.
It's the light in my bedroom- just a standard ceiling light with a twist knob on the wall. It's ancient, though. It may be original to the house, and my house is 35+ years old.
Time to upgrade JustAsking. Put in a dimmable LED light Cheap to run and virtually will last 20 years. And put in a compatible LED Dimmer. end of problems. cheers
This post was edited by Baba at January 24, 2018 8:46 AM MST
All I can say is that whenever a high-pitched squeal occurs, it usually comes down to either over-tight underwear elastic, or some reprobate stranger to AnswerMug has, goodness gracious me, cast an awful aspersion on some innocent AnswerMugger, the like of which has never been heard here before, nor ever will again.
Dimmer switches work by chopping up the AC current flowing between the switch and the light. Rather than literally “dimming” the light itself, these switches actually cause the current to undulate or flicker extremely rapidly, so that to our human eyes, it appears that there is less light.
The interrupted current can produce a vibration in the electromagnetic field within the light bulb filament or within the switch itself, which can cause a humming or buzzing noise.
JakobA the unAmerican. 