A potato battery is an electrochemical battery, or an electrochemical cell in which a chemical reaction occurs in a liquid between two different metals. When a wire is placed to connect the metals, it carries an electrical current. An electrochemical cell converts chemical energy to electric energy. This plastic clock has two compartments designed to hold potatoes or fruit. Two coils (one red and one blue) are inserted into a different potato while the green coiled wire is connected to both potatoes. This will then make the clock start working. This is an excellent demonstration clock to use in the science classroom!