Conductivity Apparatus

Comprising strips of four metals, one each of copper, iron, aluminium and brass fixed in symmetrical fashion, perpendicular to each other, on a wooden frame, with the strips meeting at the centre. The outer ends of the strips have small recesses for holding paraffin wax. As the centre is heated the wax melts at different times demonstrating the relative difference in conductivity.

Q = How do you use this apparatus?
A = Basically, to use this apparatus, you can pour a little wax from a burning candle into the wells at the ends of the metal bars, then put a marble or ball bearing into the wax before it solidifies. Once the wax has solidified you turn the apparatus over so that the marbles are on the underside. Place the apparatus on to a tripod and heat the centre (i.e. the part where the metal bars converge) gently using a low Bunsen burner flame. The marbles should start to fall off at different rates, depending on the thermal conductivity of the metal they are mounted on, as the wax begins to melt.
 The apparatus can often be re-used without the necessity of adding more wax – simply turn it back over, heat the centre and place the marbles back in. Often there will also be some wax stuck to the marbles and this will re-melt to hold them in place to be used again.

 Alternatively I think a blob of Vaseline can be used instead of wax and drawing pins pushed (flat side down) gently into the Vaseline. Again, when turned upside down and heated, the drawing pins should fall off at different rates as the Vaseline softens from the heat.