My daughter is in 3rd grade and working on her first science project. The question she came up with is how much electricity runs through potatoes, apples, lemons, and tomatoes? We need some help figuring out what might be our dependent variables and would a good hypothesis be stating which one you feel will yield the highest voltage? We are going to hook them all up to a voltmeter to see which one puts out the highest voltage. We found our real world application for the project is to use these as batteries. Any help with this would be greatly appreciated.