Potato Battery: Generate Electricity from a Vegetable

The potato battery is one of the most iconic school science demonstrations. It works because the potato’s acidic juice acts as an electrolyte, allowing ions to flow between a zinc nail and a copper coin — producing a small but measurable voltage. Two potatoes in series can power a low-power LED or even a digital clock.

What You’ll Need

• 2 medium potatoes
• 2 galvanised (zinc-coated) nails
• 2 copper coins or copper wire strips
• 3 short lengths of wire with crocodile clips
• 1 small LED or a low-power LCD clock
• Multimeter (optional but useful)

Step-by-Step Instructions

1. Prepare the potatoes: Cut each potato in half if needed to make them stable on a flat surface. Push one zinc nail and one copper coin into each potato, keeping them close but not touching each other inside the potato.
2. Check voltage (optional): Connect your multimeter’s red probe to the copper and black to the zinc in one potato. You should read roughly 0.7–0.9 V.
3. Wire in series: Use a crocodile clip wire to connect the zinc nail of potato 1 to the copper coin of potato 2. This puts the two cells in series, doubling the voltage to ~1.5 V.
4. Connect the LED: Connect the remaining copper coin (potato 1) to the LED’s long leg (positive) and the remaining zinc nail (potato 2) to the LED’s short leg (negative). The LED should glow faintly.
5. Power a clock: Replace the LED with a salvaged LCD clock’s battery terminals for a more dramatic result — the clock should run.

Safety Notes

• Wash hands after handling galvanised nails — zinc dust can irritate skin.
• Do not eat the potatoes after the experiment.
• This produces very low current — completely safe for children with adult supervision.

Tips & Troubleshooting

• If the LED doesn’t light, try reversing its connections — LEDs are polarity-sensitive.
• Lemons or oranges work even better than potatoes as they are more acidic.
• Add a third potato in series for more voltage if the LED is still too dim.