Expansion

Abstract

The experiments illustrated in Fig. 9.1 demonstrate the expansion of (a) a rod, (b) water and (c) air, when each is heated. When the rod is heated, the straw rotates. Now a small rotation of the needle results in a much larger movement of the end of the straw. If the length of the rod increases by an amount equal to the circumference of the needle, the straw will make one complete rotation. Solids expand very little on heating compared with liquids or gases and hence some arrangement like that shown in Fig. 9.1a is needed to magnify the movement.