Electrostatics Application

One common use of electrostatics is in laser printers. Laser printer use a process called xerography which applies some of the concepts used in electrostatics. This process involves a selenium coated aluminum drum, which is sprayed with positive charges from points on a device called a corotron. In the first stage, the conducting aluminum drum is grounded so that a negative charge is induced under the thin layer of positively charged selenium. In the next stage, the surface of the drum is exposed to the image of whatever is to be copied. Where the image is light, the selenium becomes conducting, and the positive charge is neutralized. In darker areas, the positive charge remains, and so the image has been transferred to the drum. The third and final stage takes a dry black powder, also known as toner, and sprays it with a negative charge so that it will be attracted to the positive regions of the drum. So, when a person wants to print on a blank piece of paper, it is fed through and the paper is given a greater positive charge than on the drum so that it will pull the toner from the drum. As the paper and toner passes through heated pressure rollers, it melts and permanently adheres the toner within the fibres of the paper.

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