The thermostat is made according to the principle that objects expand when heated and contract when cooled. Thermal expansion and cold contraction are the commonness of objects, but different objects have different degrees of thermal expansion and cold contraction. Both sides of the bimetallic strip are conductors of different substances. Under the changing temperature, the bimetallic strip bends due to different expansion and contraction degrees, and touches the set contact or switch, so that the set circuit (protection) starts to work.

This is the basic working principle and manufacturing idea of the thermostat.