ELECTROCHEMICAL CELL

AIM: To make a lemon battery to power an LED clock

BACKGROUND

A lemon battery is a type of electrochemical cell. An electrochemical cell converts chemical energy into electrical energy. In the lemon battery, there is a transfer of electrons between the zinc coating the galvanized nail that will be inserted into one end of the lemon and the copper coins that will be inserted in another end of the lemon. This is a single cell of a battery.  The zinc nail and the copper coin are called electrodes. The lemon juice is called electrolyte.

All batteries have a "+" and "-" terminal.   Electric current is a flow of atomic particles called electrons. Certain materials, called conductors, allow electrons to flow through them.  Most metals (copper, iron) are good conductors of electricity. Electrons will flow from the "-" electrode of a battery, through a conductor, towards the "+" electrode of battery.  Volts (voltage) is a measure of the force moving the electrons. The lemon conducts electricity, yet keeps the zinc ions and copper ions separate, so that the electrons in the copper coins are forced to move (generate current). It's not enough power to shock you, but the lemon can run a small digital clock.

MATERIALS

2 lemons 2 copper coins 2 galvanized nails (not all nails are galvanized or zinc-coated) 3 alligator clip wire units (alligator clips connected to each other with wire) 1 low-voltage LED clock (type that takes a 1-2 volt button battery)

PROCEDURE

1. If there is a battery already in the clock, remove it. 2. Insert a galvanized nail into each lemon. 3. Insert the coins into each lemon. Put the coins as far as possible from the nail.

A single cell of a lemon battery. (Source: http://www.hilaroad.com/camp/projects/lemon/lemon_battery.html)

4. Use an alligator clip to connect the coin of one lemon to the positive (+) terminal of the clock's battery compartment.

5. Use another alligator clip to connect the nail in the other lemon to the negative (-) terminal in the clock's battery compartment.

6. Use the third alligator clip to connect the nail in lemon one to the coin lemon two. 7. Set your clock.

Two lemon batteries combine to produce a voltage of 1.788 volts, enough to power a small LED clock. (Source: http://www.hilaroad.com/camp/projects/lemon/lemon_battery.html)

Lemon Battery - More Fun Things to Try

8. See what else your lemon battery can power. It should be able to run a computer fan. Can it light a light bulb?

9. Try substituting copper wire for the copper coins. 10. Lemons are not the only foods that can act as electrochemical cells. Experiment

with potatoes, bananas, pickles, or cola as a power source.