A few inexpensive materials are needed to make the potato-powered light bulb. These include a large potato, wire, two pennies, two galvanized nails and a flashlight battery. A knife or wire cutters are also needed. It is not necessary to use pennies or nails, however substitutions should be made of zinc and copper. The metal objects will serve as the electrodes for the batteries.
Adults should do all cutting for young children. Cut the wire into three pieces, removing any insulation if necessary. Cut the potatoes in half, then cut a slit on the top of each half. Next insert a penny into each slit and a nail into each potato half. Do not allow the pennies and nails to touch. If they do touch, remove the nails and insert them in another place. Now wrap the wire from one penny around the nail in the other potato. Wrap another wire around the other nail. Finally, touch the loose ends of wire from one penny and one nail to the base of the light bulb.
There is no electricity in the potato itself. The electrodes cause a chemical reaction which results in an electrical current. The phosphoric acid in the potato facilitates the transport of copper and zinc ions, but the potato does not participate directly in the reaction.
One potato battery produces about 1.5 volts, which is not sufficient power for a standard light bulb. To increase power, attach multiple potato batteries together. Also, other fruits and vegetables can also be used to create batteries. Lemons are particularly effective due to their high acid content.