The Photocopier

And How It Uses Electrostatics

What Is It?

A photocopier is a machine that can make paper copies of documents quickly and cheaply. Most current models use a technology called Xerography. Photocopying is used widely in schools and offices, but may go obsolete because most documents and files are sent and being kept in computers.


The photocopier was made in 1937 by Chester Carlson. He was a patent attorney in New York and part-time inventor and researcher. He invented the photocopier because his job required him to make a large number of copies of important documents. Frustrated by the difficulty and expense of copying documents, he conducted experiments with photoconductivity. The first photocopier was called the 10-22-38 Astoria. His process was later called Xerography.

How does it work with electrostatics?

1. Charging: The cylindrical drum is charged by the corona wire and has a coating of photoconductive material. A photoconductor is a semiconductor that becomes a conductor when exposed to light.

2. Exposure: The original document is illuminated by a lamp, and the white areas of the document reflect the light onto the drum. The drum becomes conductive on the spots where the light shines and discharges to the the ground. The area of the drum that is not exposed to the light from the lamp is still negatively charged.

3. Developing: The toner is positively charged, and when put on the drum to develop the image, it is attracted to and sticks onto the negative areas on the drum.

4. Transfer: The image on the surface of the drum is moved onto a piece of paper with a higher negative charge than the drum.

5. Fusing: The toner is melted and stuck to the paper by heat and pressure rollers.

How Photocopiers Work