Use in School Projects
There are numerous sets of instructions for making lemon batteries and for obtaining components such as light-emitting diodes (LEDs), electrical meters (multimeters), and zinc-coated (galvanized) nails and screws. Commercial "potato clock" science kits include electrodes and a low-voltage digital clock. After one cell is assembled, a multimeter can be used to measure the voltage or the electrical current from the voltaic cell; a typical voltage is 0.9 V with lemons. Currents are more variable, but range up to about 1 mA. For a more visible effect, lemon cells can be connected in series to power an LED (see illustration) or other devices. The series connection increases the voltage available to devices. Swartling and Morgan have published a list of low-voltage devices along with the corresponding number of lemon cells that were needed to power them; they included LEDs, piezeoelectric buzzers, and small digital clocks. With the zinc/copper electrodes, at least two lemon cells were needed for any of these devices. Substituting a magnesium electrode for the zinc electrode makes a cell with a larger voltage (1.5-1.6 V), and a single magnesium/copper cell will power some devices. Note that incandescent light bulbs from flashlights are not used because the lemon battery isn't designed to produce enough electrical current to light them.
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