How does a bimetallic strip in a thermostat detect temperature changes?

A bimetallic strip detects temperature changes by utilizing the physical properties of two different metals bonded together along their lengths. Because these metals possess different coefficients of thermal expansion, they expand or contract at different rates when exposed to temperature fluctuations.12

This difference in expansion causes the strip to flex or bend in direct proportion to the change in temperature. In the context of a thermostat, this mechanical bending is used to actuate a switch, which serves as the controller to turn a heating or cooling system on or off based on whether the room temperature has deviated from a set point. While formerly common in these control systems, bimetallic strips have largely been supplanted in modern digital thermostats by thermistors, which measure temperature via changes in electrical resistance.21