An Experiment in Equilibrium
An example of unstable equilibrium is shown in the accompanying sketch. All that is needed is a 2-foot rule, a hammer, a piece of string, and a table or bench. The experiment works best with a hammer having a light handle and a very heavy head. Tie the ends of the string together, forming a loop, and pass this around the hammer handle and rule. Then place the apparatus on the edge of the table, where it will remain suspended as shown.
Contributed by Geo. P. Schmidt, Culebra, Porto Rico, W. I.
Simple Current Reverser
Details of Reverser
On a block of hardwood draw a square (Fig. 1) and drill a hole in each corner of the square. Fill these holes with mercury and connect them to four binding posts (Fig. 1).