By Bryan Stokes II
Updated Mar 24, 2022
Although it may sound whimsical, many fruits can generate a measurable electric current. The acidic juices act as electrolytes, and when a copper wire and a zinc‑coated nail are inserted, they serve as electrodes, creating a small voltage. While the resulting current is harmless, it can be safely measured with a multimeter, making it a perfect science‑fair experiment for curious students.
Safety note: The voltages produced are typically below 1 V, so there is no risk of electric shock. Avoid inserting too many electrodes to prevent damage to the fruit.
Cut the copper wire into 3‑inch lengths. Sand the ends of the copper wire and the zinc‑coated nail to ensure good electrical contact.
Insert the copper wire and the nail into a piece of fruit, keeping the two electrodes at least 1 inch apart to reduce internal resistance.
Turn on the voltmeter (or multimeter). Connect the red probe to the copper wire and the black probe to the nail.
Record the voltage displayed. Repeat the experiment with different fruits and compile the results in a chart for comparison.
Form a hypothesis about which fruit will produce the highest voltage. Try the experiment with a glass of orange juice and compare each fruit’s voltage to a standard battery.
