The bimetallic strip is made up of two strips of different metals welded together Be cause of the difference in the coefficients of thermal expansion of the two metals, a heating of the entire strip will cause one of the metals to expand in iength more than the other. Since the strips are welded together along one entire edge, the complete will bend in the direction of the metai that the The extent of the strip is is directly proportional to the degree of temperature change one end of the be used firmly clamped while the other end remains free, the extent of the bend can(such to indicate temperature change. This is done by attaching a position trans the as an LVDT) to the free end of the strip and calibrating its displacement due to temperature change Bimetallic strips are actually used more frequently as controlling devices than as temperature-indicating devices. In this role they are used most commonly as the ther mostats which control the on-off switches of heating furnaces, and automotive auto matic chokes. As pointed out in Chapter 3, bimetallic strips are also used in some forms of circuit breakers overload currents cause the strips to bend and break the circuit connections(see Fig. 3.9)