Potato battery lesson, 10/26/15
Warm-up: what does a battery do? (Think of examples of devices that use batteries.) How does a
battery work? What is in a battery? (There are chemicals in a battery—ask if kids have heard of battery
acid. These chemicals include metals that transfer charged particles between them.)
Tie-in to previous activities: In the first lesson, we picked up salt and pepper with the charged surface of
balloons. Opposite charges on the balloon and in the salt and pepper attracted each other. Within each
grain of salt or fleck of pepper, there are charged particles, far too tiny to see even with a microscope.
Some of these charged particles, called electrons, can move, passing a current down a wire or through a
substance. This is an electric current.
In the second lesson, we looked at solar, water, and wind-powered electricity generators. Generators
work by spinning a magnet. The magnet has a force field that influences the charged particles in a wire.
When the magnet spins, the charged particles move in the wire and make a current. If we are making
electricity and want to store it to use later, we can store that energy in a battery.
Batteries store energy in the form of chemicals. Chemical reactions occur when two chemicals can
interact and release energy. This energy can be channeled into a circuit, converting chemical energy to
electrical energy. When the circuit is not complete, the chemical reaction doesn’t occur, and the energy
is stored.
Materials:
Potatoes, other fruits and vegetables (lemons, apples, carrots, oranges, vinegar…)
Wires and alligator clips
Zinc screws
Copper wires and pennies
Small LED lights
Multimeter if there happens to be one in the Haas Center (or if someone has one at work that they can
borrow)
Procedure:
Stick one screw and one penny into the potato, an inch or two apart. Don’t let them touch within the
potato. Attach a wire or alligator clip to the screw, and another to the penny. Connect the free ends of
the wires or clips to the leads of the lights. Does the light light up? Try switching the leads. Explain that
charged particles “want” to move between the zinc metal and the copper metal, but the charge has to
move through the potato and through the wires. Acids and salts in the potato carry the current of
charged particles. If there are enough particles moving fast enough, the light will turn on.
Try adding more potatoes, in parallel or in series (see below). Try different fruits and vegetables.
Diagrams from:
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Energy_p010.shtml#procedure
Basic setup
Two batteries in series (zinc connected to copper)
Two batteries in parallel (zinc connected to zinc, copper to copper)