High Quality Content by WIKIPEDIA articles! A lemon battery is a device used in experiments proposed in many science textbooks around the world. It is made by inserting two different metallic objects, for example a galvanized nail and a copper coin, into a lemon. The copper coin serves as the positive electrode or cathode and the galvanized nail as the electron-producing negative electrode or anode. These two objects work as electrodes, causing an electrochemical reaction which generates a small potential difference.