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Mains electricity and safety - Teacher Slides.pptx
The lesson slides with the teacher's notes on each slide, and every question and mark scheme built in. Built from the lesson script on 30 September 2026.
AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Mains electricity and safety
Electricity
Lesson 5 of 10
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Warm-up
Electricity
Lesson 5 of 10
Answer each one, then check.
1
What is the unit of frequency?
2
What colour is the earth wire?
3
What does a fuse do?
4
What does AC stand for?
5
What is the potential difference of the mains?
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Warm-up - Answers
Electricity
Lesson 5 of 10
1
What is the unit of frequency?
Hertz (Hz)
2
What colour is the earth wire?
Green and yellow stripes
3
What does a fuse do?
Melts and breaks the circuit if the current is too large
4
What does AC stand for?
Alternating current
5
What is the potential difference of the mains?
About 230 V
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Learning Objectives
Electricity
Lesson 5 of 10
1
State the frequency and potential difference of UK mains.
2
Explain the difference between dc and ac.
3
Identify the live, neutral and earth wires by colour and function.
4
Explain why a live wire can be dangerous even when a switch is open, and the dangers of connecting live to earth.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Electricity
Lesson 5 of 10
MAINS ELECTRICITY
Mains electricity in the UK is an alternating supply of about 230 V with a frequency of 50 Hz.
Direct pd (dc) always pushes charge in the same direction. Alternating pd (ac) repeatedly changes direction.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Direct and Alternating pd
Electricity
Lesson 5 of 10

Alternating pd changes direction 50 times each second.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
A Three-pin Plug
Electricity
Lesson 5 of 10

Colour coding makes the wires easy to identify.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
The Three-Core Cable
Electricity
Lesson 5 of 10
Learn the colour, name and job of each wire.
Wire
Colour
Job
Potential difference
Live
Brown
Carries the alternating pd from the supply
About 230 V
Neutral
Blue
Completes the circuit
At or close to 0 V
Earth
Green and yellow stripes
Safety wire: stops the appliance becoming live
0 V; only carries a current if there is a fault
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Why the Live Wire Is Dangerous
Electricity
Lesson 5 of 10
Explain why touching a live wire can be dangerous even when the switch in the appliance is open.
1
Switch position
If the switch is in the neutral wire, the live wire stays connected to the appliance
2
Potential difference
The live wire is at about 230 V compared with earth
3
Danger
A person touching it can provide a path to earth, and a current flows through the person
ANSWER
The live wire is at 230 V even when the switch is open (if the switch is in the neutral); touching it can give a dangerous current.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Live and Earth
Electricity
Lesson 5 of 10
Explain the dangers of a connection between the live wire and earth.
1
Low resistance path
A very large current can flow to earth
2
Effects
The wires heat up, which can cause a fire; a person may be electrocuted
3
Earth wire
It gives a safe path so a fuse blows or the trip operates
ANSWER
A connection between live and earth can cause a large current, overheating, fires or electric shock.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Safety Tips
Electricity
Lesson 5 of 10
Exam-ready reasons.
Fuse and switch
They go in the live wire so the appliance is disconnected from 230 V.
Earth wire
Connected to the metal case so that if the live wire touches it, a large current flows and the fuse melts.
Double-insulated appliances
Have no earth wire because they have a plastic case.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Key Terms
Electricity
Lesson 5 of 10
Direct pd (dc)
A pd that always pushes charge in the same direction.
Alternating pd (ac)
A pd that repeatedly changes direction.
Frequency
The number of cycles per second, in hertz.
Live wire
The wire carrying the alternating pd, at about 230 V.
Neutral wire
The wire that completes the circuit, at about 0 V.
Earth wire
The safety wire, at 0 V, connected to the metal case.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Electricity
Lesson 5 of 10
YOUR TASK
Plug Detective
10 minutes
A plug's wires are brown, blue and green and yellow. State the name of each wire and its job. Then say why a switch should go in the live wire.
1
Name each wire.
2
Say what it does.
WHAT A GOOD ANSWER SHOWS
Brown: live, carries 230 V. Blue: neutral, completes the circuit. Green and yellow: earth, safety wire. A switch in the live wire disconnects the appliance from the 230 V supply.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Can I...?
Electricity
Lesson 5 of 10
State the frequency and pd of UK mains.
Explain dc and ac.
Name the three wires and their colours.
State the job of each wire.
Say the live wire is at 230 V.
Explain why a live wire is dangerous with the switch open.
Explain the dangers of live-to-earth connections.
Explain the purpose of the earth wire.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Summary & Exam Focus
UK mains: 230 V, 50 Hz, ac.
Live: brown; neutral: blue; earth: green and yellow.
Earth wire only carries current if there is a fault.
Switches go in the live wire.
EXAM FOCUS
Give the colour of the live wire and state its potential difference compared with earth. (2 marks)
Brown, and about 230 V.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Mains electricity and safety
Electricity
Lesson 5 of 10
Answer all questions. Use the mark allocation as a guide to how much to write. · 15 minutes
Question 1 · 2 marks · State
State the frequency and the approximate potential difference of the UK mains supply.
Question 2 · 3 marks · Complete
The diagram shows the wires in a three-pin plug labelled A, B and C. Give the name of each wire.
Question 3 · 2 marks · Explain
Explain the difference between direct potential difference and alternating potential difference.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Mains electricity and safety (cont.)
Electricity
Lesson 5 of 10
Question 4 · 3 marks · Explain
The earth wire in a kettle is connected to its metal case. Explain the purpose of the earth wire.
Question 5 · 4 marks · Explain
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…
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 1 · 2 marks · State
Electricity
Lesson 5 of 10
“
State the frequency and the approximate potential difference of the UK mains supply.
HOW TO ANSWER IT
Command word: State. Worth 2 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 1 · mark scheme
Electricity
Lesson 5 of 10
2 marks available. Award a mark for each point made.
50 Hz
1 mark
230 V
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 2 · 3 marks · Complete
Electricity
Lesson 5 of 10

The diagram shows the wires in a three-pin plug labelled A, B and C. Give the name of each wire. (3 marks)
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 2 · mark scheme
Electricity
Lesson 5 of 10
3 marks available. Award a mark for each point made.
Earth
1 mark
Neutral
1 mark
Live
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 3 · 2 marks · Explain
Electricity
Lesson 5 of 10
“
Explain the difference between direct potential difference and alternating potential difference.
HOW TO ANSWER IT
Command word: Explain. Worth 2 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 3 · mark scheme
Electricity
Lesson 5 of 10
2 marks available. Award a mark for each point made.
Direct: one direction
1 mark
Alternating: changes direction repeatedly
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 4 · 3 marks · Explain
Electricity
Lesson 5 of 10
“
The earth wire in a kettle is connected to its metal case. Explain the purpose of the earth wire.
HOW TO ANSWER IT
Command word: Explain. Worth 3 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 4 · mark scheme
Electricity
Lesson 5 of 10
3 marks available. Award a mark for each point made.
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
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 5 · 4 marks · Explain
Electricity
Lesson 5 of 10
“
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.
HOW TO ANSWER IT
Command word: Explain. Worth 4 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 5 · mark scheme
Electricity
Lesson 5 of 10
4 marks available. Award a mark for each point made.
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
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