To show the conversion of electrical energy into mechanical energy. Consist of a star shaped copper disc of 90 mm. diameter rotatable vertically on a pair of adjustable centre plate. Disc can be adjusted on a vertical metal pillar of 75 mm. height, connected to one of the two terminals mounted on wooden base having four rubber feet. Disc dips into a small plastic mercury trough between the vertical limbs of a small horse shoe magnet. Size of base 150 x 100 mm. Operates on 4 V 1.8 A. Supplied without mercury.