Bimetallic Strip

A bimetallic strip consists of two different metals (such as brass and steel) bonded together. Because each metal expands and contracts at a different rate when exposed to temperature changes, the strip bends. This reliable mechanical movement is widely used to convert temperature changes into physical switches or indicator readings.

When a bimetallic strip is heated, the metal with the higher expansion rate grows longer than the metal with the lower rate. Because the two strips are permanently fused, the entire strip is forced to curve. The strip will always bend toward the metal with the lower coefficient of thermal expansion (making the metal with the higher expansion rate form the outer curve). Conversely, when cooled, it curves in the opposite direction.