H.2(1) - BALL AND RING

This is a simple demonstration of metal expanding when heated and contracting when cooled. When both the ring and ball are at the same temperature, the ball can easly pass through the ring. Heat the ball over a flame for a few seconds: it will not pass through the ring. A similar effect is demonstred when the ring is cooled, dipping it in liquid Nitrogen, for example.

H.2(2) - UNEQUAL EXPANSION BAR

The bar consists of a strip of brass and a strip of Invar steel each 25 cm long, cemented together and mounted in a plastic handle. It demonstrates the unequal expansion of metals. At room temperature, the bar curves slightly towards the brass side. When placed in the burner's flame, the bar will bow vigorously the other way, only to reutrn to its original shape when allowed to cool off. This property is used in the construction of thermostats.

H.2(3) - RUBBER BAND MOTOR

A bicycle wheel has its spokes replaced by stretched rubber bands. The bicycle wheel is clamped to a firm stand by its hub and is properly balanced. A heat lamp (or two) is brought close to one side of the wheel. As the rubber contracts, its shifts the weight of the rim off center. Gravity then causes the wheel to rotate.