Consists of a large board on which is mounted a low voltage electric Pump, connected to 4 mm socket terminals, which circulates the water through The circuit. The circuit is of clear plastic tubing connected to glass tubs of differing Bores representing resistance. Across the resistances is connected a detachable Manometer to show the potential difference. Following the resistance is a taper Ended tube discharging in to a funnel so that the rate of flow representing the Current may be shown.