Two different metals rolled in the form of a strip (not riveted).

Demonstrates unequal expansion of different metals when heated.

Size 150 x 12.5mm with metal handle.

A bimetallic strip bends when heated because it is made up of two metals with different rates of expansion. The metal with high thermal expansion coefficient is usually on the outside and when heated, this metal curves and forces the other metal to also curve and hence they both bend.