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Make a potato clock

Strange but true – if two potatoes are connected with some wire, and copper and zinc plates, they can run a clock or power a small light bulb.

How to build a potato clock

You will need:

  • a digital clock
  • two potatoes
  • wire
  • zinc plate
  • copper plate

Buy the parts at an electronics shop.


  • Check all the wires are securely connected (see diagram).
  • Put one copper plate and one zinc plate into each potato. The plates need to be about two centimetres deep, and about two centimetres apart.
  • Set the time on your clock – it should now be working.

How does it work?
Potatoes are full of a mineral called phosphoric acid, which reacts differently with each of the metal plates (one copper and one zinc) in your potato. Phosphoric acid dissolves the zinc plate, freeing electrons, which react with the copper plate to form hydrogen gas.

The potato acts as a superhighway of electrons between the copper and zinc plates. This flow of electrons is the electrical current that makes your clock work.