Generate Electricity with a Lemon Battery

A tingly science project from Science Buddies

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Did you know you can make a battery out of a piece of fruit? You'll be charged up on science when you feel the success of your homemade electricity! 

Key conceptsBatteriesElectric conductor

Introduction

In 1800 Alessandro Volta invented the first battery, and scientists have been hard at work ever since improving previous designs. With all this work put into batteries and all the frustration you might have had coping with dead ones, it might surprise you that you can easily make one out of household materials. Try this activity and it might just charge your imagination!

Background

Now that you know the essentials of a battery, let's examine some household materials. Aluminum foil is a good conductor—electricity flows easily through it. The human body conducts electricity as well, but not as well as aluminum foil. Electrodes are as common as copper pennies you might have stashed in your piggy bank. As for electrolytes, they are found all over the kitchen; lemon juice is just one example. A simple household battery might be easier to make than you imagined!

Materials

• At least two pennies
• Water
• A few drops of dishwashing soap
• Paper towels
• Aluminum foil (at least nine by 60 centimeters)
• Scissors
• Ruler
• At least one lemon (preferably with a thin skin)
• Plate
• Knife (and an adult's help when using it)
• At least two plastic-coated paper clips

Preparation

• Wash your pennies in soapy water, then rinse and dry them off with a paper towel. This will remove any dirt sticking to them.
• Carefully cut three aluminum foil rectangles, each three centimeters by 20 centimeters.
• Fold each strip in thirds lengthwise to get three sturdy one-centimeter-by-20-centimeter aluminum strips.
• Note: In this activity you will make a very low-voltage battery. The amount of electricity generated by this homemade battery is safe, and you will even be able to test it by touching your finger to it and feeling the weak current. Higher voltages of electricity, however, can be very dangerous and even deadly; you should not experiment with commercial batteries or wall outlets.

Procedure

• Place the lemon on its side on a plate and have an adult carefully use the knife to make a small cut near the middle of the lemon (away from either end). Make the cut about two centimeters long and one centimeter deep.
• Make a second, similar cut about one centimeter away and parallel to the first cut.
• Push a penny in the first cut until only half of it is showing above the lemon skin. Part of the penny should be in contact with the lemon juice because that is what serves as the electrolyte. This copper penny in contact with the lemon juice serves as your first electrode. Note: If your lemon has a very thick skin, you might need an adult to carefully cut away some lemon peel.
• Slide one of the aluminum strips in the second cut until you are sure part of the aluminum is in contact with the lemon juice.
• You have just made a battery! It has two electrodes made of different metals and an electrolyte separating them
• Your battery generate electricity but will only do so when the electrodes are connected with something that conducts electricity. To make a connection attach the second aluminum strip to the part of the penny sticking out of the lemon with a plastic-coated paper clip. Make sure the aluminum touches the penny so electricity can pass between the copper and aluminum.
• As soon as the two aluminum strips touch one another, electricity will be produced in the battery and flow through the strips, from one electrode to the other. Because you cannot the electricity flowing, you can try to it. Keep the two strips about one centimeter apart and touch your fingertip to them. ?
• For more electrical juice (and slightly stronger tingling sensation), you can build a second battery, identical to the first. You can choose a different spot on the lemon you just used or use a second lemon to build a second battery. Note that you only need aluminum strip to build a second battery. To connect the second one to the original find the aluminum strip of the first battery that serves as electrode. (It has its end inserted in the lemon.) Use a plastic-coated paper clip to attach the other end of this aluminum strip to the penny of the second battery. This connects the aluminum electrode of the first battery to the copper electrode of the second battery.
• Test this set of connected batteries in a similar way as you tested the single battery, bringing the ends of the two aluminum foil strips sticking out of your battery set (those that have a free end) in contact with your fingertip. (Note: If you cannot feel the tingling sensation, check if each electrode—pennies and the aluminum strips stuck in the lemon—are inserted deep enough so they are in contact with lemon juice; make sure there is firm contact between the penny and its attached aluminum strip; and that the aluminum strips are not touching one another. If all is correct, maybe you need slightly more electricity to feel tingling. You can test another person to see if he or she can feel the electricity or you can opt to add one more lemon battery to your set.)
• Extra: Now that you can detect whether electricity is generated or not, try some different configurations.
• Extra: Scientists call the way you connected your batteries in this activity "connecting batteries in series." Try it out by connecting the two copper electrodes to one another and attaching the two aluminum electrodes in the same way. (Note: You will need an extra strip of aluminum to do this.) Scientists call this "connecting batteries in parallel." Test both ways of connecting batteries and compare.
• Extra: Try different types of metals as electrodes for your batteries. ? Note that some combinations might generate electricity but the amount generated might be below your ability to feel it. Connecting two or more of these batteries might help you identify good combinations.
• Extra: You used a lemon to provide the electrolyte for your battery. Try a few from around the kitchen (with permission, of course).
• Extra: If you have an LED (light-emitting diode) available, investigate how many lemon batteries are needed to light it.

Observations and results

The battery you just made has a copper and an aluminum electrode separated by electrolyte lemon juice. It will generate electricity as soon as the electricity has a path to flow from one electrode to the other. You created this path using strips of aluminum, a material that conducts electricity well.

By connecting your battery to your fingertip, you allowed the small amount of electricity it generates to run through your body. This amount of electricity can create a tingling feeling in a fingertip. Experiences will differ from person to person. Some people might only feel the bigger signal generated by connecting several batteries in a particular way. Letting the aluminum strips touch provides a very easy way for the electricity to run from one electrode to the other, so almost no electricity will travel through your body and the tingling sensation disappears. Plastic and wood do not conduct electricity well; none will be felt when using these materials as connections. Metals, on the other hand, conduct electricity well. Different combinations of metals as electrodes will influence the amount of electricity generated. Using identical metals as electrodes will not generate electricity, however.

In this activity you made a very low-voltage homemade battery. But using commercial batteries can be dangerous—and never experiment with wall outlets!

More to exploreBatteries, from ExplainThatStuff!How Do Batteries Work?, from LiveScienceA Battery That Makes Cents, from Science BuddiesPotato Batteries: How to Turn Produce into Veggie Power!, from Science Buddies

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