The Thermostat: Controlling Temperature

Electrical appliances like irons, room heaters, and geysers are designed to automatically cut off the power if they get too hot. This setup reduces the chance of accidents. A thermostat is used in these devices to control the temperature.

The thermostat works on the principle that metal expands when heated and contracts when cooled. In a simple device, two strips of different metals (like iron and brass) are joined together. Because different metals expand at different rates when heated, the strip bends. When it bends, it moves away from the electrical circuit, breaking the flow of electricity.

Once the strip cools down and returns to its original position, the circuit reconnects and the heater starts again. This prevents the appliance from overheating. Modern thermostats use discs filled with gas instead of metal strips, as gas reacts to temperature changes much faster, making them more efficient.