# Positive and negative charges(mainly relating to copy machines)

by RuroumiKenshin
Tags: chargesmainly, machines, negative, positive, relating
 P: n/a OK, the situation in copy machines doesn't have anything to do with the wavelength. It's actually arbitrary -- here's what happens. First, we charge up the drum, which I'm going to draw as a flat plate: + + + + + + + + positive charge =============== photoconductive plate (in the dark) - - - - - - - - negative charge Now, the photoconductive plate is a special type of semiconductor which only conducts electricity when you shine light on it. Light from a lamp is bounced off the paper; the white reflects the light, the black doesn't. This is basically the definition of white/black -- we see something as black when there's no light coming from it, and white when it's an even mix of colors. So the light only gets reflected off the white parts, and hits the corresponding parts of the plate. Those parts of the plate become conductive, and the opposite charges flow across it and cancel. + + + + ============= - - - - ^^^Where the white area is in the middle. To create the original charges, we basically create a really strong voltage that can pull electrons off the top of the plate, into some wire. The voltage is got from the electric power lines in the wall.... that power is originally generated usually using some sort of magnets. See "dynamos." Ionic bonding is something that charged particles can do, but it's not relevant to electricity creation.