Applications Of Electrostatics

Question 1

Explain how a photocopier works?(4)

Answer 1

1. ) Whole surface of drum is charged positively by a rotating near a charged metal wire. (Selenium-coated drum)
2. )White light is reflected off the page to some parts of drum, making these areas conducting and losing some of their charge. Other parts of the drum, correspond to the black parts and receive no light. They remain insulating and the drum ends up with a pattern which is an exact copy of the pattern of printing on the exact page.
3. ) Fine particles of carbon powder are then attracted to the charged areas of the drum.
4. )The toner is transferred onto the photocopy as the drum rotates against the copy paper. Finally heat melts the toner and fixes it onto the paper surface.

Question 2

Explain how a laser printer works?(4)

Answer 2

1. ) Drum is positively charged
2. ) An image of the document is formed on the drum by a laser beam.
3. )Toner is applied
4. )Toner is transferred to the paper.

Question 3

How does electrostatic spray painting work?

Answer 3

Paint droplets become charged from nozzle. Car is earthed, so the charged paint particles will be attracted to the metal body of the car. The droplets all have the same charge, so they repel each other, spreading out evenly.