By Frank Whittemore Updated Mar 24, 2022
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A battery generates electricity through a chemical reaction between two dissimilar metals. In a simple lemon battery, the acidic juice acts as the electrolyte, while a copper penny and a galvanized zinc nail serve as the electrodes. When the electrodes are inserted into the lemon, a small current flows. By linking several lemon cells in series, you can produce enough voltage to power a standard 3.5‑volt LED.
Insert a galvanized nail into the far end of each of the four lemons. On the opposite end, cut a shallow slit and slide a copper penny halfway into the slit. The penny and nail should not touch each other.
Using alligator clip leads, tie the nail of the first lemon to the penny of the second lemon. Repeat this pattern to chain all four lemons together.
Attach one alligator clip to the penny of the first lemon and another to the nail of the last lemon. These will serve as the output terminals.
Turn on a voltmeter and connect its black lead to the nail of the first lemon, and the red lead to the penny of the last lemon. Verify that the combined voltage is approximately 3.5 V.
Disconnect the voltmeter. Connect the negative (black) wire of the LED to the nail of the first lemon and the positive (red) wire to the penny of the last lemon. The LED should illuminate, though the brightness will be modest.
