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.
Don Ihde called the hypothesis being 'hyped' and referred to clear evidence about the use of optical tools by, ., Albrecht Dürer and Leonardo da Vinci and others. As well the 1929 Encyclopædia Britannica  contains an extensive article on the camera obscura and cites Leon Battista Alberti as the first documented user of the device as early as 1437.  Ihde states abundant evidence for widespread use of various technical devices at least in the Renaissance and . in Early Netherlandish painting .  Jan van Eyck 's 1434 painting Arnolfini Portrait shows a convex mirror in the centre of the painting. Van Eyck also left his signature above this mirror,  showing the importance of the tool. The painting includes a crown glass window in the upper left side, a rather expensive luxury at the time. Van Eyck was rather fascinated by glass and its qualities, which was as well of high symbolic importance for his contemporaries.  Early optical instruments were comparatively expensive in the Medieval age and the Renaissance.