The University of Wisconsin has a Saturday morning program for kiddos, which I have been wanting to get to. This past Saturday we finally got to check it out.
What we discovered:
The lemon battery is called a voltaic battery, which changes chemical energy into electrical energy.
The battery is made of two different metals, steel and copper. These are called electrodes, which are the parts of a battery where electric current enters or leaves the battery. The electrodes are placed in a liquid containing an electrolyte, which is a solution that can conduct electricity (the lemon juice).
In a solution of water and an electrolyte an excess of electrons collects on one end of the electrodes. At the same time, electrons are lost from the other electrode.
A single lemon produces about 7/10 of a volt of electricity. If you connected two lemons together, you can power an inexpensive digital watch. About 1.5 volts.
Check out this link for upcoming Saturday morning events for kids at the UW Space Place.