Just about everyone has a toaster in their home, and most people use them on a pretty regular basis. These small appliances are simple devices that use electricity to create heat, which is directed toward each side of the toast (or other food) that you put in so that it can be heated up to the desired level.

Every toaster has a dial or other device that allows you to decide just how done you want your toast. These dials usually go from 1 to 10, with 1 being the lowest and 10 being the highest.

While everyone knows what that dial does, very few people really understand what changing the setting on the dial actually does to the toaster.

It is commonly thought that it is some type of timer. While few people would expect the toaster to run for 10 minutes at setting 10, many assume that it is just a timer of sorts that measures in some increment of seconds or minutes.

This is not actually the case.

Depending on the type of toaster you have, it is actually a system that either measures the heat produced by the toaster or the amount of electricity (which indirectly measures the heat) that the toaster uses. The more heat or electricity used, the more done the toast will get.

YouTuber Tom Scott made a video about this in 2014 in which he explained the older method that toasters used:

“What they have is a bi-metallic strip. Two bits of metal back-to-back, that heat up and expand at different rates, so the strip slowly curves. What you’re changing with these dials is how far that strip has to curve before it triggers the thing that pops the toast up again.”

In newer toasters, the metallic strips are gone and replaced with a capacitor. The setting on the toaster determines how fast the electrical current can flow into the toaster. Once that capacitor fills up to its limit, it triggers the toaster to cut off the power and pop the toast back up.

Both of these systems are pretty simple, and make it cheap and easy to allow the toaster to toast the bread for longer or shorter periods of time.

If you are like most people, however, you’ll find the setting you like and never change it (unless you are toasting a different type of food, such as a bagel).

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