You didn’t have to be an electrician to know that old style dimmers were inefficient. They were big. They got hot. And they were a waste of money.
The technology behind it was based on variable resistance. It sounds technical, but the concept is simple. A standard resistor is just a material that resists the flow of electric current. A variable resistor allows you to change this resistance by moving the contact arm across the resistive track.
Here’s what happens when you turn the knob.
The electric charge has difficulty push through the resistor. This struggle creates friction on an atomic level. Friction equals heat. This process causes a voltage drop in the circuit. A lower voltage reaches the load – your light bulb. Less energy in the light bulb means less light output.
It works. But it works poorly.
The resistor absorbs the excess energy that it does not send to the bulb. This energy is converted into heat. You are literally paying to heat a small piece of plastic or ceramic behind your wall. The light does not brighten. The room doesn’t get any brighter. You only pay the electricity bill for the waste heat.
These early switches were difficult to install. They were potentially dangerous because they release significant amounts of heat when near combustible materials. If you touch the faceplate during heavy use, you can burn your fingers.
Homeowners accepted this because it was the only option for a long time. It was the old way of dimming the lights. It was ineffective. It was unsafe. It was expensive to use.
We needed something better.
“The problem with this solution is that you spend a lot of energy heating the resistor, which doesn’t help you light the room, but still incurs costs.”
Industry eventually moved away from resistance-based control. The new method did not fight the current. It managed the flow in a different way. More on that later.
For now, remember: If you still have a knob that gets too hot to touch, it’s not just old fashioned. It is technically obsolete.
