How does a bi-metallic strip operate as a rate of rise detector switch?

A bi-metallic strip operates as a rate of rise detector switch by bending in response to changes in temperature. The strip is made of two different metals that expand at different rates when heated. As the temperature rises, the metal with the higher expansion coefficient pushes against the other metal, causing the strip to bend. This motion can be designed to close a contact switch, which triggers an alarm or initiates a response to the heat detection.

This mechanism allows the device to effectively monitor and respond to rapid increases in temperature, making it effective in fire detection systems. By bending to close the contact switch, it can effectively signal that a certain temperature threshold has been exceeded, indicating a potential fire hazard.