Potato Battery
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Potato Power!


Explore the science behind the popular potato battery Science Fair project! Want to know how potato batteries work? It might simply look like a couple of potatoes with clips, wires and pennies sticking out of them in all directions. But when you connect the wires and pennies – WOW!  It creates energy!  

Potato Battery Demonstration

What is a Potato Battery?

A battery is something that causes chemical energy to be converted into electricity. Batteries have a positive side (terminal) and the negative side (terminal). The negative side is the source of the electrons that gives the energy to a wire that is connected to an electronic device. Batteries power electronic devices when connected with a conductive material, such as wires.

The potato battery is a type of electrochemical battery, or cell. Certain metals (zinc in the demonstration below) experience a chemical reaction with the acids inside of the potato. This chemical reaction creates the electrical energy that can power a small device like an LED light or clock. Incredible, huh?

There are a few different ways to create batteries. Different batteries can be made from different electrolytes (acidic fruits, vegetables and liquids) and different electrodes (metals).

An electrochemical battery has these parts:
  1. Acidic Electrolyte
  2. Zinc Electrodes
  3. Copper Electrodes
  4. Connectors
Gather these supplies:
  • 3 Fresh clean potatoes – acidic electrolyte
  • 3 Galvanized nails (or screws) – they have a zinc coating and will be used as your zinc electrodes
  • 3 US Pennies (or copper wire with exposed copper end) – Pennies newer than 1982 are thinly copper-plated, while older ones have more copper. The pennies will be used as your copper electrodes
  • 5 Dual alligator clip connectors (10 actual clips total) – you can find these at most hardware or electronic stores
  • 1 LED clock that has a battery compartment
Now make a potato battery!
  1. With the close supervision of an adult, insert one nail about 1 inch into the potato end. Make sure not to poke all the way thru the potato. Use a pen to write a minus sign “-” next to the nail.
  2. Push one penny into the opposite end of the potato. Make sure most of the penny is still sticking out. Use a pen to write a plus sign “+” next to the penny.
  3. Repeat steps 1 and 2 with the other two potatoes.
  4. Number your potatoes 1, 2 and 3 and connect the potatoes in series:
    • Connect the potatoes so that the penny on potato 1 is attached to the nail in potato 2.
    • Connect the penny from potato 2 with the nail from potato 3.
    • Connect the nail from potato 1 to the penny from potato 3.
  5. Open the battery compartment to your clock. Look for the “+” and “-” signs on either side of the battery compartment.
  6. Connect the nail from potato 1 to the negative terminal inside the battery compartment of the clock and the penny from potato three into the positive terminal inside the battery compartment of the clock.
  7. Once everything is connected, observe what happens!

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Explore the science behind the potato battery

Now you’ve had fun building your potato battery and maybe even surprised a few people when that clock turned on using a potato. Now, let’s look at the how you can find out more about the real science of how it works. Some of the science might be tough to understand if you aren’t in middle school yet, but you can still give it a try.

The science behind a topic is called its scientific principles or concepts. Let’s learn a little more about the science of the potato battery by doing some background research. To do your background research, you can ask an expert, look in books or search the internet.

Below are some scientific principles and concepts of potato battery experiments that would be helpful for you to understand in order to plan your project. When searching the internet, include “kids” in your search to get age-appropriate information. For example, “kids potato battery project”.

  • Acid (Late Elementary)
  • Electrons (Late Elementary)
  • Electrolyte (Middle)
  • Electrical currents (Middle)
  • Electrically conductive (Middle)
  • Electrodes (Middle)
  • Circuit (Middle)
  • Voltage (High)
  • Current (High)
  • Oxidation-reduction (High)

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Now, think like a scientist

Scientists make observations, ask a lot of questions, then try to find ways to answer those questions. They use their understanding of scientific concepts to explore their questions. Here are a few questions for you to try to ponder now that you have learned some scientific concepts:

  • Think about all of the different toys, gadgets and tools that use batteries. What can you learn about different battery types?
  • What other fruits, vegetables or liquids do you think you could try experimenting with instead of a potato? Why?
  • Will your potato battery power your small electronic device if you only use one connecting wire? Why or why not?
  • What other types of metals could you experiment with as electrodes?
  • How do you think changing the environment would cause a change to your observations about the potato battery?
Inquiry Project

If your science fair allows inquiry projects (or demonstrations), then try to answer “why” or “how” questions as part of your project. In your own words, describe the scientific concepts that you learned about and some of the things you observed or discovered. The purpose of an inquiry is to demonstrate what you learned, observed and discovered. Demonstrations are not the same as experiments but can involve you having fun collecting data.

Experimental Project

When you do an experiment, you choose one thing to change and try to understand the results of that change. This is called Cause and Effect. If your science fair only allows experimental projects that follow “The” Scientific Method, then follow these steps:

  1.  After learning the science behind the potato battery, decide on just one thing that you will change during your experiment and what you will measure. For example, maybe you make a lemon battery instead of a potato battery.
  2. Write a detailed experimental question that makes it clear what you will change.
  3. State your prediction as a result of a change that you make.
  4. Plan how you will set up your experiment, including necessary supplies.
  5. Determine the potential health and safety risks of doing your experiment.
  6. Write down a detailed procedure that you can use when doing your experiment.
  7. Collect and record your data and observations.
  8. Display your data in a table and graph.
  9. Look for trends in your data graph.
  10. Try to explain why your data or observations turned out the way they did.
  11. Share what you learned with others.
  12. Create a project board display – refer to Project Display Tips

Want a little more help taking charge of your project? Let Mo and Pepper lead you step-by-step through an experimental project in Make Science Fair Fun®![/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

© 2022 STEM World Publishing, Public Benefit Corporation, with permission.

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