Make a lightbulb from a potato

You’ll need

Potatoes (2 per group)
Sharp knives (1 per group)
Chopping boards (1 per group)
Crocodile clips and insulated wires (4 per group)
1p coins ( 2 per group)
Long galvanised (zinc-plated) nails (2 per group)
Electric circuit lightbulb and bulb holder (1 per group)

Before you begin 

Use the safety checklist to help you plan and risk assess your activity. Additional help to carry out your risk assessment, including examples can be found here. Don’t forget to make sure all young people and adults involved in the activity know how to take part safely. 
Make sure you’ll have enough adult helpers. You may need some parents and carers to help if you’re short on helpers.

Setting up this activity  

Read our guidance on knife safety before running this activity.

Run the activity: 

Gather everyone together and explain the safety rules around using a knife. You may want to have a demonstration of the activity. Tell everyone to never walk around when holding a knife. When using it, always hold it blade side down. Everyone should take care when cutting to make sure fingers are away from the blade. Never hold anything in your hand while cutting it. Take a look at our guidance on knife safety.
Split everyone into small groups.
Give each group their own set of equipment.
One person from each group should place the potato on a chopping board and cut a slit, big enough to put a 1p coin inside, in one side of each potato.
Each penny should be placed half into each slit in the potatoes, leaving the top half of the sticking out.
Next, take a galvanised nail and place it in the opposite end of the potato to the penny. Repeat this with the other nail and potato.
Now, use the crocodile clips and insulated wires. Use one wire and clips to connect the penny on one potato to the nail of the other potato.
Use one wire to connect the penny to the bulb and the last wire to connect the nail to the bulb.
The light should hopefully turn on!

Reflection

This activity introduced you to the basics of electronics using potatoes. Have you made electric circuits before? What was it like making the circuit? Was it easy or hard or confusing or fun?

This circuit was slightly different, as we used a potato as the battery. For the past few years, a researcher called Professor Haim Rabinowitch and his colleagues have been pushing the idea of ‘potato power’ to deliver energy.

To make a battery from organic material, such as a potato, all you need is two metals. You need an anode, which is the negative electrode, such as zinc, and we used nails. The second metal is a cathode, the positively charged electrode, such as copper, and we used pennies. The acid inside the potato forms a chemical reaction with the zinc and copper, and when the electrons flow from one material to another, energy is released. Did the potato work well as a battery? Did you know a single potato can power enough LED lamps for a room for 40 days?

Next time, which vegetable would you use to power your circuit? Do you think we could ever use vegetables or similar materials as batteries in the future? What would be the benefits and the problems of this? In 2010, the world produced a staggering 324,181,889 tonnes of potatoes. They’re the world’s number one non-grain crop, in 130 countries, and a hefty source of starch for billions around the world. They are cheap, store easily, and last for a long time. However, you might deplete food stocks and compete with farmers.

What do you think would happen if you boiled the potatoes? It’s been found that by simply boiling the potatoes for eight minutes, it broke down the organic tissues inside the potatoes, reducing resistance and allowing for freer movement of electrons– thus producing more energy.

This activity may have had some challenges. Did you circuit work? Did you have any difficulties? How did you work as a team and communicate? What problems did you need to solve? Is there anything you could have done better?

Safety

All activities must be safely managed. You must complete a thorough risk assessment and take appropriate steps to reduce risk. Use the safety checklist to help you plan and risk assess your activity. Always get approval for the activity, and have suitable supervision and an InTouch process.

Sharp objects: Teach young people how to use sharp objects safely. Supervise them appropriately throughout. Store all sharp objects securely, out of the reach of young people.
Food: Remember to check for allergies, eating problems, fasting or dietary requirements and adjust the recipe as needed. Make sure you’ve suitable areas for storing and preparing food and avoid cross contamination of different foods. Take a look at our guidance on food safety and hygiene.

Make it accessible

All Scout activities should be inclusive and accessible.