In this project, you will build a battery using a potato, a zinc electrode, and a copper electrode. You will measure the voltage with a voltmeter and investigate how the voltage is related to the electrode spacing and surface area (Figure 1).
How does a potato battery work? The zinc (on the surface of the galvanized nail or screw) and copper (in the penny or wire) react together to produce chemical energy. The potato acts as an electrolyte between these two dissimilar metals. This chemical energy is then converted to electric energy as the current flows through the circuit.
This basic experiment is based on the use of a potato, however, many fruits (lemons and limes, for example) and vegetables can also work as potential batteries! For the zinc electrode, a large galvanized nail or screw works well. Nails with a thick, rough zinc texture are preferable to galvanized nails that are smooth.
Step 1: Push both the nail and the wire deep into the potato, as illustrated above in Figure 1. Measure the voltage output by the potato battery with a voltmeter. Now, wasn’t that easy?
Step 2: Seriously, though, experiment with different metals, electrode depths, and electrode spacings to obtain the greatest voltage possible from the potato. Try increasing the copper surface area by wrapping the wire around a copper penny.
Step 3: Try other vegetables or fruits and compare voltage output with the same electrode metals.
It can be difficult to power a load with a single “potato” battery, so don’t expect to light up an incandescent lamp, power a hobby motor, or do anything like that. Even if the voltage output is adequate, a potato battery has a fairly high internal resistance which causes its voltage to “sag” badly under even a light load. With multiple potato batteries connected in series, parallel, or series-parallel arrangement, though, it is possible to obtain enough voltage and current capacity to power a small load.
Learn more about the fundamentals behind this project in the resources below.
In Partnership with NXP Semiconductors
by Robert Keim