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Things to do online and at home.

A selection of online and hands on activities that relate to the science behind this project. No special equipment required.

Tomato battery

Combine a tomato with some copper and zinc and you have yourself a battery. By using a pair of headphones you will be able to hear the electricity created.

You will need
  • A tomato
  • A galvanised nail or paper clip
  • Some copper wire
  • A pair of head phones
Directions
  1. Stick the nail / paperclip in to the potato, about half an inch away stick the copper wire in.
  2. Put on the headphones.
  3. Look at the plug from the headphones; you will see that the metal part is made of two or three sections.
  4. Touch one piece of metal to one section of the headphones and the other piece of metal to one of the other sections. If the plug has three sections, then you may have to try touching different sections for this to work.

What can you hear?

What’s going on?

The acid in the tomato reacts with the two different metals in different ways. It causes the copper wire to gain electrons and the nail or paper clip to lose electrons. The balance is restored by touching the metals to the headphone plug. This completes an electrical connection between the metals so electrons can flow from the copper to the nail/paper clip.

This is exactly how a battery works – converting chemical energy to electrical energy.

Finally this electrical energy is converted into sound energy by the speakers in the headphones and you can hear it.

More

The taste of a tomato is partly down to the amount of acid it contains, follow this link to find out more.

Warning!

Do not eat any tomato after you have used it for this experiment.

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eat the tomato

Posted by oda at Nov 24, 2008 12:15 PM
why can't I eat the tomato?

Tomato battery

Posted by Project Member at Dec 15, 2008 12:56 PM
Hi, I'm not sure exactly why it is advised to not eat the tomato after using it for this experiment but I will try to find out and here are a couple of guesses.
A) It's unlikely people are going to wash their materials e.g. the nails and wire before using, so they may not be very hygenic.
B) Galvanised nails are covered by Zinc which in small ammounts is actually necessary in our diet (see the page on Tomato Nutrition by following the SuperVeg link above) but in larger amounts may be harmful.

Thanks for the interesting question.