Introduction
Four lemon batteries wired in a series charge a capacitor. When connected to a calculator, the capacitor supplies sufficient voltage and current to power the calculator.
Equations
Oxidation: Zn → Zn2+ + 2e-
Reduction: 2H+ + 2e- → H2
To Conduct Demonstration
- Insert a strip of copper and a strip of zinc in each lemon cell.
- Connect wires (with alligator clip ends) from the positive (copper) terminal of one lemon cell to the negative (zinc) terminal of another lemon cell such that the four cells are wired in series. The remaining copper and zinc electrodes are then connected to a calculator (or music card).
Note that pre-1982, all-copper pennies will also work, but modern zinc-core pennies are not as effective.
Safety and Disposal
There are no safety hazards or special disposal procedures required for this demo.