Lemon Battery

Batteries use chemical reactions to create an electric current. In 1800 Alessandro Volta made the first battery by layering copper and zinc in a jar of salt water. The chemical reaction created the first steady supply of electricity. The steady supply of electricity from batteries is used to power all sorts of electrical devices such as toys, light bulbs, radios, calculators and cars. Following Volta’s example we can make batteries, too.

 

Materials

6 lemons

7 alligator clips

6 pennies

6 large metal paperclips

Knife

Voltmeter

Light emitting diode (LED) that requires low voltage and low current

Calculator that requires low voltage and low current

 

What To Do

Prepare the lemons for use in the battery by placing the lemons one by one on a flat surface and firmly pushing down on them with one hand while rolling them back and forth. This is to break up the insides of the fruit so the juices can flow more easily. Use a knife to make two small incisions in the middle of each of the lemons. The cuts should be about ½ inch long, deep enough to reach the juicy insides of the fruit, and about ½ inch apart. In each lemon insert a penny into one of the slits so only a small part of the coin remains on the outside of the lemon. Do the same with a paperclip in the other slit. Line up all of the lemons so that the inserts alternate in order (i.e. penny, paperclip, penny, paperclip, penny . . . ).Use an alligator clip to connect the penny from the first lemon to the paperclip of the next lemon. Continue connecting the lemons by using alligator clips to bridge from lemon to lemon, connecting pennies to paperclips. The first and last lemons in the row will have a paperclip and a penny that are not wired to the rest of the battery. Connect an alligator clip to each one to create the leads for the battery. Turn the voltmeter to DC mode and test the lemon battery by connecting the lead wires to the voltmeter. If the voltage is very low test each lemon separately using the wires connected to the penny and paperclip in each lemon. Lemons that are not working well can be adjusted by squeezing them to break up more of the tissue inside, moving the penny and the paperclip, or refastening the wires to the penny and the paperclip in slightly different locations. Also, check that the penny and paperclip do not touch each other directly. Once the lemon battery is working well, as confirmed by the voltmeter, it can be used to power the LED. Gently bend the legs of the LED away from each other. Connect the wire that leads from the paperclip to the side of the LED that is flat and has the shorter leg. Connect the wire from the penny to other leg of the LED. Dim the lights in the classroom and the glow from the LED should be visible.

 

Questions

1. What else might the lemon battery be able to power?

2. What other types of fruits might be used to make batteries?

3. If more lemons were used to make the battery would the amount of electricity it produced be different? Would the voltmeter show a higher, lower, or the same reading?

 

Summary

Electricity is the flow of electrons. Electron flow can be produced by some chemical reactions, including this one between zinc from the paperclip, the copper from the penny, and the citric acid in the lemon juice. The chemical reaction takes some positively charged zinc ions from the paperclip, leaving behind an excess of negatively charged electrons. The penny becomes positively charged by drawing positive ions from the lemon juice solution, and then the electrons flow from the negatively charged paperclip to the positively charged penny. This flow of electrons is the electricity produced by the lemon battery.

 

Extension

What else can the lemon battery power? Remove the battery from a simple calculator and attach wires to the positive and negative terminals for the battery. Connect the lead from the paperclip to the negative terminal and the lead from the penny to the positive terminal of the calculator. Does the calculator work? Try a few calculations.

 

Sources

"How Science Works," Judith Hann, Reader’s Digest, Dorling Kindersley Limited, 1991, p. 151.

"Fruit Cell" in "Awesome Experiments in Electricity and Magnetism." Michael DiSpezio, Sterling Publishing Company, 1998, p. 102. ISBN 0-8069-9819-9

© S. Olesik, WOW Project, Ohio State University, 2001.