Make a Potato Clock

Using potatoes to create an electrical current may seem impossible, but it’s actually rather easy to produce an electrical charge using only some potatoes and a few different types of metal. You can use this battery to power a clock for a short time for a science project or just for fun. The makeup of the potato conducts electricity, but keeps the zinc ions in the nail and the copper ions apart, forcing the electrons to move from one to the other, which generates an electrical current. You can make a potato clock using two or more potatoes.

Steps

Making a Two Potato Clock

  1. Gather the necessary materials. Before you can get started putting together your potato clock, you first must gather the items you’ll need. You can likely buy most of these items at your local hardware or hobby store, except the potatoes which will need to be purchased at a grocery store.[1]
    • 2 potatoes
    • 2 pieces of heavy copper wire
    • 2 galvanized nails
    • 3 alligator clip assemblies (each should be two clips connected by wire)
    • A simple, low voltage digital clock
  2. Remove the batteries from the digital clock. When completed, the potatoes will connect to the positive and negative ends of the battery terminals inside the clock instead of the batteries. You will want to keep the battery cover removed so you can easily access the terminals with your wires.[2]
    • If the clock does not have the positive and negative battery connectors labeled, mark them yourself using a permanent marker based on the way the batteries were connected.
    • If they are labeled, the positive end will be marked with a “+” and the negative will be labeled with a “-“.
  3. Insert one nail and one short piece of copper wire into each potato. Begin by labeling the two potatoes as 1 and 2, this will help you to differentiate them as you move forward with the experiment. Then press one nail about an inch into each potato near the end. Once the nail is secured, press a piece of copper wire into the opposite end of the potatoes, as far from the nail as possible.[2]
    • Each potato should have one nail and one copper wire sticking out of opposite ends.
    • Make sure the nail and wire aren’t touching inside the potato.
  4. Use the alligator clips to connect the potatoes and clock. You will be connecting each of the potatoes together and to the clock utilizing the three alligator clip units. In doing so, you will establish a circuit that includes the clock and each potato that will allow electrical current to pass through. Connect each of the following:[1]
    • Connect the copper wire in the first potato to the positive (+) terminal in the clock's battery compartment using the first alligator clip.
    • Connect the nail on the second potato to the negative (-) terminal in the clock.
    • Use the third alligator clip unit to connect the nail in the first potato to the copper wire in the second one.
  5. Check the connections and set the clock. As soon as you connect the third alligator clip unit to the two potatoes, the clock should turn on. If it fails to do so, check each of the connections to ensure they are tight and there is good metal on metal contact in each.[2]
    • This method will not last for very long, so after confirming that it works, you may want to disconnect it if you hope to enter the clock into a science fair or present it to your class.

Building a Three Potato Clock

  1. Begin by gathering your materials. As with any experiment, you must begin by gathering the materials you will need. You can purchase most of these materials at your local hardware or hobby store, or you may even have some of them at home already. Gather the following:[3]
    • 3 potatoes
    • 3 copper strips, or you can use pennies
    • 3 galvanized nails
    • 4 alligator clip units connected with wires (10 total clips)
    • 1 low current digital clock
  2. Place one nail in each potato. Just like making a two potato clock, each potato will need one galvanized nail inserted into it. Place the nail near the end of the potato and press it in about an inch. Then repeat for the other two potatoes.[3]
    • Make sure the nail doesn’t break through the other side of the potato.
    • Ensure you don’t press the nail into the potato in such a way that will make it touch the penny or copper strip you will insert next.
  3. Insert a penny or copper strip into each potato. Press a penny or copper strip into each of the potatoes on the opposite end from the nail. If you are using a penny, make sure to press it into the potato so half of the penny is still visible above the surface of the potato skin so you can attach an alligator clip to it in the subsequent steps.[4]
    • If using a copper strip, make sure you don’t insert it so far into the potato that it comes into contact with the nail.
    • Try to separate your copper from the nail as much as possible in the potato.
  4. Connect the potatoes in a series. Once you have a galvanized nail and a piece of copper in the ends of each potato, you can connect them to one another in a series to produce more electricity. Place the three potatoes in a row in front of you and use the alligator clip units and wires to connect them to one another sequentially. Make sure the potatoes are lined up in the same way, with the nails all on one side and the copper on the other.[3]
    • Attach an alligator clip to the copper end of one potato, then connect it to the nail on the next one.
    • Repeat that process until each of the outside potatoes are connected to the middle one with one wire.
  5. Connect the potatoes to the clock. The two outer potatoes should only have one wire connecting them to the middle potato. Now attach an alligator clip unit to the remaining nail on one potato, and another separate clip to the remaining piece of copper in the other potato.[4]
    • Attach the alligator clip unit coming from the nail to the positive terminal inside the battery compartment of the clock.
    • Attach the alligator clip unit coming from the nail on the final piece of copper to the negative battery terminal.
  6. Check the connections and set the clock. Once both clips are attached to the positive and negative battery terminals, the clock should turn on. If it doesn’t, check each of the connections to ensure they are attached tightly and there is good metal on metal contact.[4]
    • Once connected securely, the clock will come on.
    • You may want to disconnect it to avoid depleting the chemical energy in the potatoes if you need to show the experiment at a fair or in class.

Troubleshooting Your Potato Clock

  1. Check the wire connections. If your clock fails to work, there may be an issue with one of the connections between the potatoes or the clock. Make sure that each connection is tight and that there isn’t any material separating the metal from the alligator clip from the galvanized nail or the piece of copper. You also need to ensure the connections are made in the correct order: wires should connect negative to positive. The nail on one potato should connect to the copper on the next and so forth.[3]
    • Try replacing pennies with strips of copper to ensure a strong connection.
    • Make sure each alligator clip is firmly attached where it belongs.
  2. Add another potato. If everything is connected properly but the clock is still not working, it may be because your potatoes aren’t producing enough voltage to power the clock. You can use a multimeter or voltmeter to check the amount of voltage being produced by your potato batteries if you have them, or you can try adding another potato to your battery chain to increase the amount of power it produces.[3]
    • Connect an additional potato just as you connected the first ones: run an alligator clip unit from the copper of one potato to the galvanized nail on the next, then from the copper on that potato to the clock or the next potato.
    • If another potato still does not make the clock work, there is either an issue with the connection or the clock.
  3. Soak the potatoes in Gatorade. Soaking the potatoes overnight in Gatorade can increase their conductivity and help ensure your potato powered clock works. Gatorade contains electrolytes that can help conduct the electrical current through each potato, but you’ll need to soak the potatoes overnight in order to ensure the electrolytes reach the center of the potato.[5]
    • Gatorade also contains phosphoric acid, which adds to its conductive properties.
  4. Swap the potatoes out for conductive fruit. If you cannot make your potato powered clock function, you may want to try swapping the potatoes out for another conductive fruit. Lemons and oranges both work as great replacements for potatoes when conducting this experiment. Place the nail and copper into the fruit just as you did the potato.[3]
    • Rolling the fruit on the table first can help break down the interior of the fruit, allowing fluid to travel more easily, and as a result, the electrical current too.
  5. Ensure you have the right materials. Using the incorrect materials can make it far more difficult or even impossible to correctly assemble your potato clock. Look over your materials and the packaging they came in so you can make sure you have exactly what you think you have.
    • Make sure the package you purchased the nails in says they are galvanized. While most nails are, this experiment will not work if they are not.
    • Ensure the clock you purchased runs on 1-2 volts and takes a traditional “button-type” battery. You can see how many volts it requires on the product information on the package.[2]

Warnings

  • Do not eat the potatoes afterwards.
  • Young children should be supervised when performing this experiment - nails and wires are sharp and can cause injury if handled incorrectly. Removal of batteries should also be supervised.

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 http://www.kidzworld.com/article/4726-how-potato-batteries-work
  2. ↑ 2.0 2.1 2.2 2.3 http://www.kidzworld.com/article/4726-how-potato-batteries-work
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 https://www.teachengineering.org/activities/view/cub_energy2_lesson04_activity2
  4. ↑ 4.0 4.1 4.2 https://www.teachengineering.org/activities/view/cub_energy2_lesson04_activity2
  5. ↑ http://freshpotatoes.com.au/wp-content/uploads/2014/05/10plus_SeedsforSchools_PotatoPower.pdf
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