The two metals are chosen to have different rates of expansion and contraction with rise and fall of temperature.
They are bonded together side by side.
When heat is applied one gets longer than the other and the bi-metallic strip [ bends as a result.
This bending can be used to cause a thermostat to turn on the air conditioning.
Circuit breakers use this effect to shut off an overloaded circuit where a slight overload is ... (More)