Why a tomato has more electric value then a potato?

Answer 1

The science fair projects which involved sticking copper and zinc plates demonstrates a simple chemical reaction call an electrolytic reaction, which is a simple battery. Before the question can be answered, we have to investigate how electrolytic reactions occur. The reaction occurs due to two materials (the electrodes) that have different affinities (or attraction) to electrons, which differs enough that one is willing to give up an electron and the other is willing to accept one. These reactions usually do not happen by themselves, and only occur when a "salt bridge" is between the two electrodes, which provides free, nonreactive ions to carry charge from one electrode to the other. The more ions there are in the salt bridge, the faster the reaction, which brings us to the original question. The two produce provides the necessary salt bridge through their acidity, which is the measure of free H+ ions in solution. Since a tomato is more acidic (4.1 pH) than a potato (~5 pH), there are more free ions floating around, thus the electrolytic reaction occurs faster. The faster the reaction occurs the more electrons are moving, thus the higher the voltage generated by this impromptu battery.