BAR AND GAUGE
PR-80
This apparatus is used for illustrating expansion by heating and contraction by cooling.
It consists of a mild steel bar 110×10 mm (length), mounted on a rod with a wooden handle, overall length approx. 280mm; with a cast metal gauge.
The gauge has a cut-out that allows for a sliding fit over the ends of the bar, at room temperature.
Also the gauge has a hole (10mm bore) in one arm that allows the bar to pass endways, only when cold.
However when the metal bar is heated, it does not fit into the gauge . When allowed to cool, the bar will fit into the gauge again.
Thus, heating the bar and then comparing it to the gauge provides an excellent visual demonstration of thermal expansion.