This machine is used in a library to make copies of damaged maps without handling the original many times. Fig. 1 shows the main stages inside the copier. A...
Question 1 Report
This machine is used in a library to make copies of damaged maps without handling the original many times. Fig. 1 shows the main stages inside the copier. A rotating drum is given a positive charge. Bright light reflects from the pale areas of the map onto the drum. Negatively charged toner particles are then brought near the drum, before paper passes through the machine.
(a) State what happens to the charge on a bright area of the drum when light falls on it. [1]
(b) Explain why negatively charged toner particles stick to the dark areas of the drum. [3]
(c) Describe how the toner image is transferred from the drum to the paper. [3]
(d) State why a metal casing connected to earth is used around the charging parts. [2]
(e) Explain why the copier should not be used if its casing has a crack and a wire is exposed. [2]
Answer Details
(a) On a bright area of the drum, the positive charge is removed, so that area becomes uncharged or has less positive charge remaining. [1]
(b) Dark map areas receive little or no light, so the corresponding drum areas remain positively charged. Negatively charged toner particles are attracted to these oppositely charged areas and stick there. [3]
(c) The paper is given a positive charge, or another charge that attracts the toner. Toner transfers from the drum to the paper, then heating melts or fixes it permanently onto the paper. [3]
(d) The earthed metal casing provides a path for excess charge to flow to Earth. This reduces charge build-up and the risk of sparks. [2]
(e) A crack with an exposed wire could allow someone to touch a live conductor. This could cause electric shock because current could pass through the body. [2]
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