Fig. 1 shows part of a photocopier. A rotating metal drum is given a positive charge. Light reflected from a printed page removes charge from selected regio...
Question 1 Report
Fig. 1 shows part of a photocopier. A rotating metal drum is given a positive charge. Light reflected from a printed page removes charge from selected regions of the drum. Negatively charged toner particles are then released close to the drum. The toner forms the pattern that will later be transferred to paper.
(a) State which regions of the drum attract the negatively charged toner particles most strongly. [1]
(b) Explain why those regions attract the toner particles. [2]
(c) Describe why the toner must later be heated onto the paper. [2]
Answer Details
(a) The negatively charged toner is attracted most strongly to regions that remain positively charged, namely the dark regions not exposed to light. [1]
(b) Toner particles are negatively charged. Opposite charges attract, so the positively charged regions exert an electrostatic force on the toner. [2]
(c) Heating melts or softens the toner. It then sticks permanently to the paper, so the copied image does not rub off easily. [2]
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