In fixed-temperature switch controls, heat levels are varied by applying different voltages (110V or 220V) to different coils of different resistances, as shown in figure 4-C. These are usually push-button or rotary switches with fixed settings such as warm, low, medium and high. There are also fixed-temperature switches that vary the voltage going to the heating elements to maintain fixed, pre-set temperatures.
Then the bimetal cools (along with the elements) until the contacts close again. The bimetal heats (along with the element) until the contacts open. When the heating element is on, the heater inside the switch is on. (see figure 4-C) A cam attached to the control knob changes spring tension on the bimetal, which changes the amount of heat needed to open the switch. This switch has its own little heater inside, which heats a bimetal switch.
To maintain a set temperature in an electric cooktop, the element is cycled on and off, usually by a switch called an infinite switch, so named because it theoretically provides an infinite number of heat settings.