How a printer works

How the drum of the printer works

The drum of the printer gets a positive charge from the charged corona wire (some printers use charged roller instead of the corona wire but they work the same.) As the drum spins a small laser beam shines to discharge certain points. This way the laser "draws" images and texts as a result of an electrostatic charges, this is called an electrostatic image. This process can also work with the charges being reversed. After the pattern is done the printer coats the drum with a black powder called the toner. Since the toner has a positive charge it attaches to the negative parts of the drum but not the positive. With the pattern set on the drum it rolls over the paper
HP LaserJet 1022 and How Laser Printers Work