Potatoes do not store electricity; they have chemical properties which have the potential to transfer energy between specific materials to work as an electrochemical cell. The common view of potatoes is that they store chemical energy or potential chemical energy for people as they consume them. Potatoes (electrochemical cells or batteries) also have stored chemical energy which can be converted to electrical energy to run a clock or turn on a small light bulb.
To use the potential chemical energy in potatoes to create electricity, to types of metal are needed. These metals are zinc and copper. These two metals are inserted into a potato to create a chemical reaction to generate an electrical current or flow of electricity (kinetic energy). Wires are connected from the zinc and copper metals to a clock or light bulb to complete an electrical circuit to permit the flow of electricity.
Science of Potato Batteries
The potato itself has a mixture of starches, salts, and water. The salt in the potato interacts with the water and releases ions. Ions are atoms that have an electrical charge. Salt releases two electrically charged ions; a sodium ion with a positive charge and a chlorine ion with a negative charge.
Positive electrical charges and negative electrical charges attract each other. The positive charge in a metal (for example zinc) will attract negatively charged electrons. The other metal (for example copper) with a negative charge reacts with the chlorine in the salt within a potato. This attraction of positive and negative electrical charges causes the flow of electrical current or electricity.
Building a Potato Powered Electrical Circuit
Students use problem solving and science process skills as they complete the following potato battery investigation.
Materials (per group)
- 2 potatoes
- 2 lengths copper uninsulated wire (6 cm long)
- 2 small galvanized nails (must be galvanized for the zinc) or 2 pieces of zinc (6 cm long)
- 3 insulated copper or aluminum wires with alligator clips on both ends (30 cm long)
- 1 LED clock that works with 1 – 2 vdc (volts direct current) with battery removed
- 1 small light bulb that works using 1 -2 vdc
- 1 light bulb socket
Supplemental Materials
- 2 pennies
- 2 nickels
- Asparagus Stalks
- Celery Stalks
Procedures
Part 1
- Insert a galvanized nails in potato 1 and potato 2.
- Insert an uninsulated copper wire into potato 1 and potato 2, about 8 cm from galvanized nail.
- Connect one insulated copper wire with alligator clips between a galvanized nail in potato 1 and copper wire in potato 2.
- Connect one insulated copper wire with alligator clips between the copper wire in potato 1 to the positive terminal of the clock’s battery compartment.
- Connect one insulated copper wire with alligator clips between the galvanized nail in potato 2 to the negative terminal of the clock’s battery compartment.
- Students record their group observations.
Part 2
- Screw the light bulb in the light bulb socket.
- Disconnect the clock from the potatoes.
- Connect potato 1 to one connection point on the light bulb socket.
- Connect potato 2 to one connection point on the light bulb socket.
- Students record their group observations.
Part 3
Students are provided supplemental materials to test hypotheses developed in questions 5, 6, and 7.
Student Questions
- What types of energy were used?
- What types of energy transformations occurred?
- What do you think would happen if the zinc nails were moved closer to the copper wires in the potatoes?
- What do you think would happen if only one potato was used instead of two?
- Would other vegetables (steer students to asparagus and celery) work as batteries? Why or why not?
- What would happen if the copper wire was replaced with a penny?
- What would happen if the galvanized nail was replaced with a nickel?
Twenty questions to ask students in science projects provide additional ideas for question development.
Making Connections
As students complete this investigation it is important for them to make connections with the types of energy and energy transformations were used in this investigation such as electrochemical, potential, kinetic, electrical, electrochemical to electrical, electrical to light, etc. Also, what connections there are with either endothermic and/or exothermic reactions in this investigation (basic chemistry in a bag)? A student’s ability to make connections between science concepts is critical for developing a greater understanding of science.
David R. Wetzel - Dr. David Wetzel's experience includes more than 25 years in continuing, adult, and teacher education.
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