When life gives you lemons, a lemon battery is not really the first thing that comes to mind when you think of the yellow citrus fruit. Nor does a potato battery come to mind when you look at a bunch of fries, but it is actually surprisingly easy to turn a lemon/ potato, two copper and zinc electrodes and a length of wire into something that produces an electrical current.
In this type of battery the electrical current is produced due to a chemical process which takes place which is referred to as an electrochemical reaction. This is actually the reaction that happens in many batteries.
In the lemon there is an acid called citric acid and this acid starts to dissolve the zinc and copper. The potato contains phosphoric acid which also dissolves the two metals.
When a zinc atom dissolves the atom loses two electrons which are negatively charged particles.
When the circuit is completed with a wire to join the two electrodes the electrons will flow from the zinc to the copper. If you then put a low powered digital clock or possibly a LED light into the
circuit you could power it. Although you may need to string a couple of cells (cells make up a battery) together this will increase the voltage and it will be able to power the LED.
There are other ways to increase the voltage produced by a single cell. For example if instead of using a copper coin you could use a small coil of copper the size of the coin and this will greatly increase the surface area speeding up the chemical reaction and thus increasing the voltage.
You can even turn this experiment into a science fair project by changing different aspects of your set up and measuring the voltage. Lemons are not the only fruit that will work. You could try apple and oranges and tomatoes, anything acidic, but the question is which one is most suited to producing the most voltage.