The photoelectric effect occurs when light causes electrons to fly off atoms. An equal number of electrons to protons gives an atom a net charge of 0. If I left a piece of metal in the sun for a long time, that would mean a large number of electrons would fly off. This should, in theory, give the part of the metal exposed to sunlight a positive net charge NOTE: Although I say in theory, the purpose of this post is not to debate a theory. Rather, I am trying to understand a question that I cannot resolve.