AQA GCSE Physics Physics Paper 1 (Foundation), November 2020: Question 3

8 marks · Standard Demand difficulty · Short Answer

Calculate electrical power and energy transfers, identify AC mains properties and electrical safety hazards in a lighting circuit.

Practise this question

Question

Figure 5 shows a lighting circuit with a lamp connected to a neutral wire and a live wire containing a switch. Five sub-questions follow: 03.1 asks to tick one box for the UK AC mains frequency from four options (20 Hz, 50 Hz, 60 Hz, 100 Hz). 03.2 asks to tick one box identifying the graph of an alternating potential difference from three oscilloscope traces. 03.3 asks to calculate power given potential difference 230 V and current 0.020 A using power = potential difference x current. 03.4 asks to calculate energy transferred given potential difference 230 V and charge flow 180 C using energy transferred = charge flow x potential difference. 03.5 asks to describe the hazard and risk when an electrician replaces the light switch in Figure 5.
Question text

03 Figure 5 shows part of a lighting circuit in a house.

Figure 5

03.1 What is the frequency of the ac mains electricity supply in the UK?

[1 mark]

Tick ( ) one box.

20 Hz 50 Hz 60 Hz 100 Hz

03.2 The mains electricity supply has an alternating potential difference.

Which diagram shows an alternating potential difference?

[1 mark]

Tick ( ) one box.

03.3 The potential difference across the lamp is 230 V.

The current in the lamp is 0.020 A.

Calculate the power output of the lamp.

Use the equation:

power = potential difference × current

[2 marks]

Power = W

03.4 The potential difference across the lamp is 230 V.

Calculate the energy transferred by the lamp when 180 C of charge flows through the

lamp.

Use the equation:

energy transferred = charge flow × potential difference

[2 marks]

Energy transferred = J

03.5 An electrician needs to replace the light switch in Figure 5.

Describe the possible hazard and the risk to the electrician of changing the light

switch.

[2 marks]

Hazard

Risk

Mark scheme

Show the mark scheme The mark scheme provides answers for questions 03.1 through 03.5, allocating 1 mark each for 03.1 (50 Hz) and 03.2 (the first alternating waveform graph), 2 marks for 03.3 (substitution and answer 4.6 W), 2 marks for 03.4 (substitution and answer 41,400 J), and 2 marks for 03.5 (hazard: live wire or high potential difference; risk: electric shock or electrocution).

Question 3

AO /

Question Answers Extra information Mark

Spec. Ref.

03.1 50 Hz 1 AO1

4.2.3.1

03.2 AO1

1 4.2.3.1

03.3 P = 0.020 × 230 1 AO2

4.2.4.1

P = 4.6 (W) 1

03.4 E = 180 × 230 1 AO2

4.2.4.2

E = 41 400 (J) 1

03.5 Hazard: 1 AO3

live wire 4.2.3.2

or

high potential difference ignore current in his body

Risk: 1

electric shock allow (electrical) burn

or

electrocution allow death (by electric shock)

allow 1 mark for hazard and risk

in incorrect order

Total 8

How to answer it

Mains Electricity and Electrical Safety

What this question tests

This question assesses your knowledge of domestic UK mains electricity (frequency and alternating potential difference), application of electrical equations for power and energy transfer, and your ability to identify electrical safety hazards and risks.

Question 03.1

Frequency of UK Mains Electricity

✅ Correct Answer

Tick the box for 50 Hz .

💡 Key Knowledge

  • The UK domestic mains electricity supply has a frequency of 50 Hz.
  • This means the alternating current changes direction 50 times every second.
  • The standard UK mains potential difference is approximately 230 V.
Mark: 1 mark | AO1 (Recall)
Question 03.2

Alternating Potential Difference Waveform

✅ Correct Answer

Tick the first box (the sinusoidal wave crossing above and below the 0 V line).

💡 Key Knowledge

  • Alternating Current (ac): Continuously changes direction (represented by a wave going above and below the 0 V line).
  • Direct Current (dc): Flows in one direction only (represented by a straight horizontal line either above or below 0 V).

❌ Common Errors

Students often confuse ac waveforms with dc straight lines, or pick the third graph which shows a rectified or pulsating wave rather than standard sinusoidal mains ac.

Mark: 1 mark | AO1 (Recall & Understanding)
Question 03.3

Calculating Power Output

📐 Step-by-Step Calculation

  1. Identify equation: power = potential difference × current
  2. Substitute values: P = 230 × 0.020
  3. Calculate result: P = 4.6 W

🧠 Exam Technique

Always show your substitution clearly, even for simple calculations. If you make a mental arithmetic error, working out marks can still be awarded.

Power = 4.6 W (Units are usually given in the answer line, but it is great practice to include them).

Marks: 2 marks | AO2 (Application)
Question 03.4

Calculating Energy Transferred

📐 Step-by-Step Calculation

  1. Identify equation: energy transferred = charge flow × potential difference
  2. Substitute values: E = 180 × 230
  3. Calculate result: E = 41,400 J

❌ Common Calculation Traps

Watch out for large numbers! Do not panic at 41,400 J. Double-check your multiplication using standard column multiplication or your calculator twice.

Marks: 2 marks | AO2 (Application)
Question 03.5

Electrical Safety: Hazard and Risk

✅ Correct Answer

Hazard: Live wire OR high potential difference.
Risk: Electric shock OR electrocution (allow electrical burn or death).

🧠 Exam Technique & Examiner Insight

Examiners emphasize the strict distinction between a hazard (the source of potential harm, e.g., the exposed live wire) and a risk (what happens to the person, e.g., electric shock).

Note: If a student accidentally swaps hazard and risk (e.g., puts hazard as electric shock and risk as live wire), the mark scheme allows 1 mark to be awarded for both concepts being present overall.

Marks: 2 marks | AO3 (Analysis & Safety Context)

Topics

Physics · P2: Electricity

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.