RING & BALL 18mm diameter (0201) A simple and economical device for demonstrating the thermal expansion of solids. Comprises an annular brass ring mounted on an insulated handle and a captive brass ball secured to the ring handle through a chain and having diameter just smaller than the ID or the ring. When cold, the ball easily passes through the ring but does not pass on heating. When heated to the same extent, the ball still passes through the ring showing the "expansion of a hole" effect. Qty :