Separate the two potatoes. Each potato works as a "galvanic cell", releasing electrical energy through chemical reactions.[1] Call one potato A (or 1) and the other potato B (or 2).
The bulk of the potato serves as a case for the cell, holding everything in place. The potato juice serves as the "electrolyte," in which charged atoms and molecules called "ions" dissolve and can flow over time.[2] The dilute phosphoric acid in it also provides hydrogen ions for the reaction.
Some atoms (or molecules) strongly attract extra electrons and become negatively charged ions, called anions ("an-ions"); others are easily stripped of some electrons and become positively charged "cations" ("cat-ions"). Each element attracts electrons with different force, due to the differing charge of protons with which their nucleus attracts electrons and the manner in which the marginal "valence" electrons arrange themselves around the nucleus and other electrons.[3]. The potato juice has dilute phosphoric acid[4], some of which dissolves dissociated into as hydrogen cations (basically) and phosphate anions.[5]