A bimetallic strip is shown in the figure below. It is one of the most commonly used methods to determine temperature. It consists of a thin rectangular strip formed of two diverse metals which are bonded back to back. Both the metals employed in a bimetallic strip experience dissimilar thermal expansion rates.
Hence, with the increase in temperature, one metal will expand faster than the other metal. As a result, a bending effect is created on the strip. This bending of the strip can further be employed to activate a switching device.