Potato clock. Two potatoes being used to provide electrical current sufficient to power an electronic clock. The potatoes are being used as electrolytic cells, the electrolyte being natural phosphoric acid. Four electrodes - two copper and two zinc - are placed in the potatoes and connected together. Zinc atoms on the electrode are oxidised, losing two electrons per atom and dissolving into solution. The electrons pass through the wires to the copper electrode where they combine with hydrogen ions to liberate hydrogen gas. The movement of electrons between electrodes form the current.