Mainly for fun but also as educational experiment. I use this well known 'battery from vegetable' experiment to show my son, that electricity can be found everywhere. He could not belive, that potatoes can flesh LED lamp.
This experiment was also described by my physics teacher in high school. So I think that any other physics teacher can show potatoes battery to his/her students.
What will be needed:
Potatoes - more is better (but it could be also tomatoes, cucumbers.. the best are lemons. They allow to achieve highest voltage)
Nails/screws: normal and copper one.
Step 1: Electrodes
First You need to insert two nails into every potato. Two different ones: copper and normal nail in each vegetable.
Step 2: Connecting
Get some short wires and connect copper nail from one potato with normal nail in other potato.
After this step You will end with 'the battery chain' with two free nails at the beginning and at the end.
Step 3: Cathode&anode - Electricity
Connect voltmeter to the first and last nail in 'battery chain'.
That's all, now You can see that there is some voltage.
Try to connect LED to this voltage and You will see light.
The power from potato battery is very low, so You won't be able to run very much devices on it. You could try LCD calculator, but for more power consuming devices try to use lemons instead of potatoes. Lemons generates lower voltage, but higher power.
I recommend to do more experiments on this topic and do some research in google. There are for example some tutorials on how to light the campfire with lemon.
How it works ?
It is because electrons flows between two electrodes (nails). More about it You can find on wikipedia: https://en.wikipedia.org/wiki/Lemon_battery
That's all. If You find it fun or interesting, watch (and subscribe) my other videos on Youtube or read my other Instructables.