Electrostatics in Xerography

Study Notes

Xerography (Photocopier)

Xerography derives from the Greek word "xeros," meaning "dry writing."
The main component of a photocopier is a drum made of aluminum, which is a strong conductor.
The drum is coated with selenium, which acts as a photoconductor: insulating in the dark but conducting when exposed to light.
A positive charge applied to the selenium remains until the drum is exposed to light, causing the charge to neutralize.
Dark portions of the document produce areas on the drum that retain positive charges; light areas become conductive.
A temporary positive charge image is formed on the selenium surface that corresponds to the document.
Toner, a dry black powder negatively charged, adheres to the positively charged areas of the drum.
The toner is transferred to paper, and the image is permanently fixed by melting the toner with heated rollers.

Inkjet Printer

Inkjet printers utilize electrostatics to position tiny ink droplets on paper.
Ink droplets receive an electric charge within the cartridge before being ejected.
The charged droplets are precisely directed across the paper in specific lines.
The ink dries rapidly, allowing clear printing of text and images on paper.
Droplets have a diameter of approximately 5 micrometers and are ejected through charged plates called deflectors.
Deflectors create an electrostatic field at the printhead's exit, controlling the trajectory of the droplets.
The printhead operates by moving horizontally across the paper, depositing ink one dot at a time to form the final image.

Description

This quiz explores the principles of electrostatics as applied in xerography, the process used in photocopiers. Understand how materials like aluminium and selenium interact in the copying process, and learn about the underlying physics that makes xerography possible.