Download Lemon Battery Mini Lesson

Lemon Battery Mini Lesson
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, oranges, or other fruit
5 bags containing 1 lead with alligator clip, one paper clip, and one penny
1 bag containing same as above plus items below and extra supplies
Knife
Voltmeter
Light emitting diode (LED) that requires low voltage and low current
battery
Preparation
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. It is helpful if the slits are above and below one another rather
than side to side.
What To Do
Give each student a lemon. Demonstrate with the remaining lemon(s).
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 . . . ).
Have the students use an alligator clip to connect to the penny. Check to be sure all
of the clips attach only to the penny!
Have each student pass the free end of their lead (wire) to the person on their right.
(Direction doesn’t matter, just be consistent).
Students should take the free end of the lead just handed to them and connect it to
their paperclips
You the instructor should not attach the lead handed to you to your paperclip.
Instead, explain that you have made a battery and that you will test it with a
voltmeter. Be sure the switch is to the left on the voltmeter.
Use the snap on your own lead to connect to the – side of the black voltmeter.
Use the free alligator lead from the person to your left to connect to the positive side
of the voltmeter. The arm should swing to between one and two volts. If it doesn’t
move, have each student in turn gently pull out and push back in the paper clip and
penny and check that the clips are firmly attached.
[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.
Electrons are much more strongly attracted to copper than zinc, and will move along
the wire toward the copper penny.
The penny draws 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.