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Lemon Power: How Can You Make a Battery Out of a Lemon?

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Author: Janice VanCleave

Problem

How can you make a battery out of a lemon?

Materials

• 18-gauge copper wire (smaller-gauge wire will work)
• wire cutters
• paper clip
• coarse sandpaper
• lemon

Procedure

1. Ask your adult helper to strip 2 inches (5 cm) of insulation from the wire. Cut off the bare metal with the wire cutters.
2. Then, ask your adult helper to straighten out the paper clip and cut a 2-inch (5-cm) piece from one end.
3. Use the sandpaper to smooth any rough edges from the wire and the piece of paper clip.
4. Gently squeeze the lemon with your hands until it feels soft. Do not rupture the lemon.
5. Push the pieces of paper clip and wire into the lemon so that they are as close as possible without touching.
6. Moisten your tongue with saliva, and touch the tip of your wet tongue to the free ends of the wires.

Results

A slight tingle may be felt and a metallic taste is detected.

Why?

The lemon battery you have created is called a voltaic battery. A voltaic battery, like all batteries, changes chemical energy into electrical energy. It is a battery made up of two different metals called electrodes (part of battery where electric current enters or leaves the battery), which are placed in a liquid containing an electrolyte (a substance whose water solution can conduct electricity). In a solution of water plus an electrolyte, such as the acid in the lemon, an excess of electrons collects on one of the electrodes, at the same time electrons are lost from the other electrode. Touching the electrodes to your tongue closes the circuit and allows an electric current to flow. The tingle felt and the metallic taste is due to the movement of electrons through the saliva on your tongue.

Let's Explore

1. Do the types and combinations of metals affect the results? Repeat the experiment using different combinations of metals such as a copper penny and a nickel, or a nickel and a paper clip (steel). Ask an adult to cut slits in the lemon so you can insert the coins. Use new coins or scrub old coins with a dish scouring pad.
2.
1. Would a different kind of acidic food produce the same results? Repeat the original experiment using other citrus fruits such as grapefruit or oranges. Try noncitrus acidic foods such as tomatoes.
2. Would food not considered to be high in acidic content produce the same results? Repeat the experiment using foods such as bananas or potatoes. Science Fair Hint: Photographs along with the results of each experiment can be used as part of a project display.

Show Time!

A single lemon battery will produce about 0.7 volts. If two lemon batteries are connected together, they supply enough voltage to power a digital watch. Build and display a lemon-powered watch by using pennies (copper) and paper clips (steel) as the electrodes. Ask an adult to cut slits in the lemons to hold the electrodes. Insert the penny and paper clip as close as possible in each lemon without touching. Use small flexible wire, such as 22-gauge, and alligator clips to connect the penny in the first lemon to the paper clip in the second lemon. Remove the battery from an inexpensive digital watch. Using two separate 18-gauge wires and alligator clips, connect one wire to the paper clip in the first lemon and the second wire to the penny in the second lemon. Touch the free ends of these two wires to the battery contacts on the watch. To observe the face of the watch, stand it on its side and place a mirror in front of it.

Check it Out!

In 1792, Alessandro Volta, a professor of physics at the University of Pavia, Italy, discovered that chemical action between two metals could produce electricity. Find out more about Volta's experiments for producing an electric current. One of Volta's most famous experiments—called the Voltaic pile—represented the first real electric storage battery. How is a Voltaic pile constructed? Describe Volta's experiment that he called "the crown of cups."