Electricity and Magnetism > EMF and Current
zinc and copper strips
Measure emf of voltaic cell consisting of zinc and copper strips inserted in a lemon. Measure current to show that the internal resistance is large. Lemon battery can be used to power a buzzer.
Use Radio Shack buzzer # 273-065. Buzzer will sound with as little as 0.5 V, 0.03 mA.
Lemon: V = ~0.9 V, I = ~0.5 mA. Maximize current by rolling/pressing lemon on table, putting metal strips in deep and close together.