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How to Make a Potato Clock - Science Project

Instructor: Amanda Robb
In this lab, you'll be learning about electrochemistry. We'll study how potatoes can be used as a source of energy to power a small battery powered clock. After this lab, you'll be able to discuss alternative sources of energy to use in place of batteries.

Introduction

Goal: To use the chemicals in potatoes to power a small clock
Age: Middle school and up
Safety concerns: You'll need a sharp knife to insert the metal into the potato. Be extremely careful or get an adult to help you.
Time: 1 hour

What do you need to power a clock? You're probably thinking batteries. Batteries use chemical energy and convert it to electricity, or the flow of electrons, tiny negatively charged particles. Although we typically think of electricity for small devices as coming from batteries that we find in stores, there are other ways to harness the chemical energy needed as well.

Today, we're going to be testing a cheap version of a battery, a potato. You probably have only considered a potato as a food source, but today we're going to see if we can harness the energy in the potato to power a small clock. Before you get started, think about why this experiment might work? Would more potatoes provide more power? Why or why not?

Materials

  • 2 large russet potatoes
  • Sharp knife
  • 3 pieces of copper wire
  • 2 galvanized nails (nails coated in zinc)
  • Alligator clips
  • One small digital clock (the kind that takes a 1V circular battery)

Steps

Safety tip!! Handle the knife with care and get an adult to help you with this step.

1. Carefully cut slits, one in each potato. Then, insert a copper wire into each of the slits.

2. Now insert the nails, one into each potato, on the ends opposite the wires.

3. Open up the battery compartment of the clock and remove the battery if needed. Leave this open because we'll need to connect the wires to the metal.

4. Using alligator clips, connect the wire from one potato to the positive terminal in the clock's battery compartment.

5. Again, with alligator clips, connect a wire from the nail in the other potato to the negative terminal in the clock.

6. Lastly, connect the nail on the first potato to the copper wire on the second potato.

Experiment setup
Potato Clock

7. Observe what happens to the clock. Does it turn on?

Troubleshooting

You need to use the exact metals suggested here, copper and a nail covered in zinc. A steel nail will not work. Make sure all the connects of the wires and clips are secure. If your wires are loosely connected, the electricity will escape and you won't have enough power for your clock.

If your clock still isn't turning on, test it out with a real battery and make sure that it's operational.

Discussion Questions

What happened when you connected the circuit?

What do you think is in the potato that generates electricity?

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