Electricity
3 marks · EasyA student describes a domestic plug as having a live wire, a neutral wire, and an earth wire.
Give the function of the earth wire in a plug.
Explain why the case of some electrical appliances is made from plastic.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) To provide a path for current to earth if the case becomes live, preventing electric shock.
(b) Because plastic is an insulator, making the case prevents users from receiving an electric shock.
Common mistakes: Mixing up live and earth roles
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states function: provides a safe path to earth for fault current.
B1 (b) · 1 mark · Plastic is an insulator.
B2 (b) · 1 mark · Relates use of an insulator to prevention of electric shock.
Worked solution
a) The earth wire provides a path for current to flow safely to the ground if the case becomes live.
b) Plastic is an insulator. Making the case from plastic prevents users from receiving an electric shock if a live wire touches the case.