Mr. Potato Clock

Potatoes are great mashed, roasted, baked or in clocks! Yes, you read that right… potatoes are nature’s tastiest battery. Parents, you may remember this activity from watching any of the classic science shows, like Mr. Wizard’s World, Bill Nye the Science Guy or even Beakman’s World. Show your young scientist the power of nature!

Vocabulary

• Battery–
  (noun) an electric cell or connected electric cells providing electric current.
• Current–
  (noun) a stream of electric charge.
• Charge–
  (noun) the amount needed to load or fill something; a quantity of electricity.
• Voltage–
  (noun) potential difference measured in volts.
• Terminal–
  (noun) a device attached to the end of a wire or cable or to electrical equipment for making connections.
• Galvanized–
  (verb) to coat (as iron) with zinc for protection.
• Electrochemical–
  (noun) a science that deals with the relation of electricity to chemical changes and with the change of chemical to electrical energy or vice versa.

Materials

• Two potatoes
• Two short pieces of heavy copper wire
• Two common galvanized nails
• Three alligator clip/wire units (alligator clips connected to each other with wire
• One simple, low-voltage LED clock that functions from a 1- to 2-volt button-type battery

Activity

1. Remove the battery from the battery compartment of your LED clock.
2. Make a note of which way the positive (+) and negative (-) points of the battery are positioned.
3. Number the potatoes as one (1) and two (2), then carefully insert one nail into each potato.
4. Insert one short piece of copper wire into each potato as far away from the nail as possible.
5. Use one alligator clip to connect the copper wire in Potato 1 to the positive (+) terminal in the clock’s battery compartment.
6. Use one alligator clip to connect the nail in Potato 2 to the negative (-) terminal in the clock’s battery compartment.
7. Use the final alligator clip to connect the nail in Potato 1 to the copper wire in Potato 2, and set the clock!

Explanation

A potato battery is an electrochemical battery, otherwise known as an electrochemical cell, which is a cell where chemical energy is converted to electric energy by a spontaneous electron transfer.

In the case of the potato, the zinc in the nail reacts with the copper wire. The potato acts as a sort of buffer between the zinc ions and the copper ions. The zinc and copper ions would still react if they touched within the potato but they would only generate heat.

Since the potato keeps them apart, the electron transfer is forced to take place over the copper wires of the circuit, which channels the energy into the clock.