Hi just made a potato battery, using a cupper coin and zink nails (not connected in any way, just pit in a nail and 3 inches appart a penny), I was just wondering what is the chemistry/physics theory here? Potatoes contain phosphoric acid H3PO4 Is it the acid in potatoes that oxidize the 2 metals? or id it the standard electrode potential? Electrode potential for Zn Zn(+2) + 2e ---> Zn(s) = -0,76 V (so it want's to be oxidized and should reduce Cu (+2) to Cu (s) because Cupper has a positive electrode potential. But does the acid oxidize both metals in the first place?