how does a heat control switch work?

Question

Like on an appliance. A hot plate.

Answer 1

Nearly all such controls operate on the principle that metal expands as it gets hot, the hotter, the more expansion. Some controls are a straight or curved piece of metal or strips of metal, others like a furnace thermostat have a coil spring like a watch, furnace controls have a little curvedm thin coin shaped piece of metal that pops over center when it reaches a certain temp. All are going to make or break a circuit when they get hot enough to move a certain distance.

A hot plate is going to warm up until the little piece of metal expands enough, then it will bend enough to break the electrical switch contact. When it cools down, it makes the circuit again and this cycle repeats itself many times.

Answer 2

http://en.wikipedia.org/wiki/Bi-metallic_strip