AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Mains electricity and safety
Mains electricity and safety · Electricity · Lesson 5 of 10 · 14 marks · 15 minutes
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Instructions
• Answer all the questions.
• Write your answers in the spaces provided.
• The marks for each question are shown in brackets - use this as a guide to how much to write.
• The answers are on separate pages at the back. Attempt every question before you look at them.
• Answer all questions. Use the mark allocation as a guide to how much to write.
Question 1 STATE (2 marks)
State the frequency and the approximate potential difference of the UK mains supply.
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(Total for Question 1 = 2 marks)
Question 2 COMPLETE (3 marks)
The diagram shows the wires in a three-pin plug labelled A, B and C. Give the name of each wire.
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(Total for Question 2 = 3 marks)
Question 3 EXPLAIN (2 marks)
Explain the difference between direct potential difference and alternating potential difference.
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(Total for Question 3 = 2 marks)
Question 4 EXPLAIN (3 marks)
The earth wire in a kettle is connected to its metal case. Explain the purpose of the earth wire.
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(Total for Question 4 = 3 marks)
Question 5 EXPLAIN (4 marks)
A person touches the live wire in a broken appliance, but the switch in the appliance was off. Explain why the person could still receive an electric shock, and why connecting the live wire to earth is dangerous.
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(Total for Question 5 = 4 marks)
TOTAL FOR PAPER = 14 MARKS
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Answers and mark scheme
Check your answer only once you have written one.
Question 1 (2 marks)
50 Hz and about 230 V.
• 50 Hz 1 mark
• 230 V 1 mark
Question 2 (3 marks)
A: earth (green and yellow), B: neutral (blue), C: live (brown).
• Earth 1 mark
• Neutral 1 mark
• Live 1 mark
Question 3 (2 marks)
A direct pd always causes charge to flow in the same direction. An alternating pd repeatedly changes direction.
• Direct: one direction 1 mark
• Alternating: changes direction repeatedly 1 mark
Question 4 (3 marks)
It is a safety wire. If the live wire touches the case, a large current flows through the earth wire, which stops the case from becoming live, and the fuse melts.
• Safety wire 1 mark
• Stops the case becoming live 1 mark
• Only carries current if there is a fault, so the fuse melts 1 mark
Question 5 (4 marks)
The live wire is at about 230 V, and if the switch is in the neutral wire the live wire is still connected to the supply, so the person provides a path to earth and a current flows through them. A connection between live and earth gives a very large current which can cause a fire or shock.
• Live wire is at about 230 V 1 mark
• Switch may be in the neutral wire, so live remains connected 1 mark
• Current flows through the person to earth 1 mark
• Live to earth: very large current causing heating, fire or shock 1 mark