Jordan

A rice cooker specifically does not use a thermostat to tell when it is done cooking rice. As it heats up the water evaporates and stops absorbing heat energy, this then heats the magnet which holds a circuit closed. A heated magnet loses magnetism and then opens the circuit turning the device off. An over however does use a thermostat because the temperature it needs to achieve varies while a rice cooker only cooks rice and the magnet can be designed for one temperature only.