FINDING THE VOLTAGE OF DIFFERENT TYPES OF POTATO BATTERIES
Samantha Dietrich
Cary Academy
ABSTRACT
The purpose of the experiment was to find which form of potato, being used as a battery
produces the most energy and lights an LED the best. It was hypothesized that the
generic Idaho potato would produce the most energy and light an LED the best as it
was the kind of potato most often used as a battery. A section of copper wire was stuck
into the potato, then a zinc nail next to it. The metals were then attached to an LED via
alligator-clip wires. To measure the voltage, the battery was hooked up to a digital
multimeter. The voltage was found and recorded. This was done to all of the potatoes.
The blue potato produced the most voltage at .946 V. The Idaho potato battery
produced .819 V. The sweet potato battery produced .88 V. The baked potato battery
produced .888 V. The French fry battery produced the least energy at .81 V.
INTRODUCTION
The purpose of this experiment was to find which form of potato, being used as a
battery, produces the most energy and lights an LED the best. Typically, these are
made by using a potato, and sticking a zinc plated nail into it, and sticking a copper wire
segment next to it. Alligator clip wires are clipped to each of the metals. When the two
loose ends of the wire are attached to a small light bulb or LED, it supposedly lights up.
Potato batteries are electrochemical cells, in which chemical energy is converted into
electrical energy through a spontaneous electron transfer (this occurs when an electron
moves from an atom/ molecule into another atom/molecule. The potato separates the
zinc (nail) and copper (penny) ions. If the zinc and copper had been touching in the
potato, they only would have generated heat. With the potato between them, the
electron transfer must occur in the copper wire, channeling the energy into the light
bulb/LED.
Electrochemical reactions most often involve an electron transfer. The passage of an
electric current causes or accompanies them. In most cases, it involves an electron
transfer between a solid and a liquid. Mostly, chemical reactions involve heat or light,
but not another form of energy. There are some chemical reactions that produce
electricity rather than heat, or light.
The potato battery is a cell, and is made up of the electrodes, which electrons enter and
exit from (the nail and the penny) and an electrolyte, which allow electrons to flow
through them (the chemicals in the potato). Chemical reactions between these are what
change the chemical energy to electric energy. The zinc plated nail becomes the
negative side of the battery and the penny becomes the positive. Caused by a chemical
reaction between the metal and the potato, electrons gather at the negative side of the
battery, but are lost at the positive side. This causes some electrons from the negative
side of the battery to move towards the positive side of the battery. The current creates
enough energy to light up a small light bulb or LED.
The potential difference between two places in a circuit or electric current is voltage. It
can also be thought of as the amount of energy released when a charge moves from
one place to another in a current. The greater the voltage, the more energy is released.
If there is voltage between two places on a current, then electrons will flow through the
current. A greater voltage makes a greater current. The greater the current, the more
electrons move through the wire each second.
The resistance of an object affects the amount of electrons that can move through the
wire. Conductors, such as copper or iron, have a small enough resistance so that
electrons can move through them. However, copper has a much lower resistance than
iron, so more electrons can flow through it at a time. Insulators, on the other hand, have
so much resistance that electrons cannot pass through them at all, Wood, cloth, and
paper are all insulators. In the potato battery, the copper penny, the wire, the nail, and
even the chemicals in the potato are conductors. If there was an insulator in between a
wire and a penny in the battery, the light bulb would not light, because the electrons
would not be able to get through the material to power the light bulb.
The sweet potato was a sort of reddish, orangeish, brown color, and pointy on both
ends. It was rough and scratched. It was 14.5 cm, and had a mass of 312 g. The normal
Idaho potato was brown, long, and had round ends. It felt rough, hard and had dips in
the skin. It was 16.5 cm and had a mass of 448.1 g. The blue potato was purplish
brown, round, rough and hard. It had a few blemishes in its skin. It was 6 cm, and had a
mass of 89 g. The baked potato was dark brown, long and round on both ends. It was
rough, and soft. The dips in the skin were the same as the ones the normal Idaho potato
had. It smelled like French fries, and was 13.5 cm. The French fries were light brown,
long rectangular prisms. They were soft and soggy.
It was hypothesized that the normal Idaho potato would produce the most energy as a
battery and light an LED the best, because it is the most often used to make a potato
batteries. The sweet potato and the blue potato may have less of the chemical in them
that produces electricity when it reacts with the copper and zinc. The baked potato and
the French fries were cooked, and liquid turns to steam when heated up, so some of the
chemical may have left them when they were cooked.
MATERIALS AND METHOD

Copper wire segment

Zinc plated nail

Baked potato

French fry

Sweet potato

Normal Idaho potato

Blue potato

Red LED

Multimeter

Alligator clip wires
First the zinc plated nail was stuck into the potato, and then the copper wire segment
was stuck next to it. Alligator clip wires were clipped to each the zinc plated nail and the
copper wire segment. The loose ends of the wires were clipped to the red LED to see if
it lit. Then the Alligator clip wires were taken off of the nail and the copper wire. A digital
multimeter was used to measure the amount of voltage the potato battery produced.
This was repeated for each of the potato variations. The control of the experiment was
the Idaho potatoes. The independent variable was the kind of potato used. The
dependent variable was the amount of volts produced. Controlled variables included
type of wire, type of electrolyte, and type of LED used.
RESULTS AND DISCUSSION
Amount of Volts Produced (V)
1
0.95
0.9
0.85
0.8
0.75
0.7
Idaho
Blue
Sweet
Baked
French Fry
Type of Potato
The Idaho potato battery produced .819 V. The blue potato battery produced .946 V.
The sweet potato battery produced .88 V. The baked potato produced .888 V. The
French fry produced .810 V. The maximum amount of volts produced in the experiment
was the blue potato at .946 V. The minimum amount of volts produced was the French
fries at .810.
CONCLUSION
The hypothesis was that the normal Idaho potato would produce the most energy and
light an LED the best, but it was not confirmed. The Idaho potato battery produced only
.819 V. The blue potato produced much more, .946 V, the most energy produced from
any of the other potato batteries. None of the potato batteries could actually light an
LED anyways, so it was an incorrect hypothesis. The reason this might have happened
is that the way that the potato battery produces electrical energy is by way of a chemical
reaction between the electrolytes and the chemicals in the potato. Since the potato
doesn’t have much liquid in it, the chemical may not be present as much as in
something like a lemon, which is also often used as a battery. The blue potato seemed
to have more liquid in it than the Idaho potato, so it would produce more energy. The
experiment could be improved by using even more types of potatoes, such as mashed
potatoes, to see if it makes a difference. Future experiments that could be performed
are using citrus fruits instead of potatoes, as such fruits as lemons, limes, and oranges
have more liquid, and therefore more chemical reaction, then the potatoes. The
experiment could also be done on different fruit juices to find if that could also work.
REFERENCES
California Science Center. "Lemon light." California Science Center. California Science
Center. 2013. Web. January 28, 2014.
Champagne, Andrew. Electricity and Magnetism. Austin: Holt, Rinehart, and Winston,
2007. Print.
Kidsworld. "How Potato Batteries Work." Kidzworld. 2014. Web. January 27, 2014.
Robert Lamb. "Lemon Batteries and Potato power." How Stuff Works. How Stuff Works
Inc.2014. Web. January 27, 2014.