This part of the process loosely resembles how a camera takes a picture. If you've read How Photographic Film Works , you know that when film is exposed to light, the energy of the photons causes chemical changes in the silver halide grains coating the film. This creates a negative image of what you see through the viewfinder. With a photocopier, however, you end up with a real image created from a pattern of positive charges left after exposure to light. And while you have to develop film using special chemical processes and print it on light-sensitive photographic paper, the photocopier produces a visible image with only dry ink, heat and regular paper.
Voltage is applied to the aluminum core of the drum.
Since light renders selenium conductive, current can flow through the photoconductive layer while the drum is being illuminated, and the electrons released by the atoms are quickly replaced by the electrons that form the current flowing through the drum. The exposed areas of the drum rotate past rollers encrusted with beads of toner. Tiny particles of toner are pressed against the drum's surface. The plastic-based toner particles have a negative charge and are attracted to areas of positive charges that remain on the drum's surface. The corona wire passes over a sheet of paper so that the paper's surface becomes electrically charged.