AQA GCSE Combined Science: Trilogy Physics Paper 1 (Higher), June 2025: Question 5
14 marks · Standard Demand difficulty · Short Answer
State properties of mains electricity and the colour codes of wires, explain the effect of laptop use on charging time, and calculate the time taken to charge the battery while in use.
Practise this questionQuestion
Question text
05 Figure 5 shows a laptop computer, and a charger plugged into the mains supply.
Figure 5
05.1 Give the potential difference and frequency of the UK mains electricity supply.
[2 marks]
Potential difference V
Frequency Hz
05.2 The cable that connects the charger to the plug contains two wires that have
coloured insulation.
The cable does not contain an earth wire.
Name each wire in the cable.
Give the colour of the insulation covering each wire.
[2 marks]
Name of wire Colour of insulation
Name of wire 17 Colour of insulation
05.3 The input to the charger is an alternating potential difference.
The output from the charger is a direct potential difference.
Describe the difference between an alternating potential difference and a direct
potential difference.
[2 marks]
A student is using the laptop computer.
The student notices that the battery has no stored energy.
The student quickly plugs the charger into the laptop and continues to use the laptop.
05.4 The laptop charger provides a constant power to the laptop.
The laptop takes longer to charge when the student uses the laptop than when the
laptop is not used.
Explain why.
[2 marks]
05.5 The potential difference across the laptop circuit is 15 V.
The average current in the laptop circuit when it is being used is 4.8 A.
The laptop charger provides a constant power of 97 W.
The maximum energy that the battery can store is 225 kJ.
Calculate the time taken to fully charge the battery from zero when the laptop is
used continuously.
*17*Use the Physics Equations Sheet.
Give your answer in hours.
[6 marks]
Time = hours
Mark scheme
Show the mark scheme
Question 5
AO /
Question Answers Extra information Mark
Spec. Ref.
05.1 230 (V) allow about 230 (V) 1 AO1
6.2.3.1
50 (Hz) 1
AO /
Spec. Ref.
05.2 live – brown 1 AO1
6.2.3.2
neutral – blue 1
AO /
Spec. Ref.
05.3 alternating (potential difference) 1 AO1
continuously changes direction 6.2.3.1
direct (potential difference) is 1
always in the same direction
AO /
Spec. Ref.
05.4 energy / power is transferred by 1 AO2
the laptop (when being used)
(so) the power delivered to the allow (so) the rate at which 1 AO3
battery is reduced energy is transferred to the
battery is lower
6.1.1.4
– – 8464/P/1H – 6.1.2.1
AO /
Spec. Ref.
05.5 P = 15 × 4.8 1 AO2
6.2.4.1
P = 72 (W) 1 6.2.4.2
6.1.1.4
ΔP = 97 – 72 = 25 (W) 1
225 000 subsequent marks may be 1
25 = awarded if an incorrect / not
t
converted value of E is used.
t = 9000 (s) 1
t = 2.5 (hours) 1
Total Question 5 14
How to answer it
AQA GCSE Physics: Mains Electricity & Power Calculation
This question assesses core recall and application skills from Topic 2: Electricity:
- Recall of standard UK mains potential difference ( 230 V ) and frequency ( 50 Hz ).
- Wire colours and names in a two-core cable ( live = brown , neutral = blue ).
- The clear physical distinction between alternating (a.c.) and direct (d.c.) potential difference.
- Qualitative reasoning around energy conservation, power diversion, and charging rates.
- A multi-step 6-mark calculation linking P = V × I , net power, energy conversion ( kJ to J ), and time conversion ( seconds to hours ).
UK Mains Electricity Supply Values
Recall of standard voltage and frequency values [2 Marks]
✅ Correct Answers
- Potential difference: 230 V (allow "about 230") [1 mark]
- Frequency: 50 Hz [1 mark]
💡 Key Knowledge
- UK domestic electricity is supplied as alternating current (a.c.).
- Units are already provided in this question ( V and Hz ), but you must remember them when writing numerical answers from scratch.
❌ Common Errors
- Writing US values (e.g., 110 V or 60 Hz).
- Swapping the numbers around (e.g., writing 50 V and 230 Hz).
🧠 Exam Technique
These two numbers are purely recall facts from the specification. Make sure they are committed to memory before entering the exam.
Two-Core Cable Wire Identification
Names and colours of insulation in a two-wire cable [2 Marks]
✅ Correct Answers
- live – brown [1 mark]
- neutral – blue [1 mark]
💡 Key Knowledge
Standard UK 3-core plug wiring colours:
- Live wire (Brown) – Carries alternating potential difference from the supply (~230 V).
- Neutral wire (Blue) – Completes the circuit (at or near 0 V).
- Earth wire (Green/yellow stripes) – Safety wire; not present here because the charger is double-insulated.
🧠 Exam Technique & Memory Hook
- bLue goes to the Left (Neutral).
- bRown goes to the Right (Live).
- Striped goes to the Top (Earth).
❌ Common Errors
- Naming the earth wire despite the question explicitly stating: "The cable does not contain an earth wire."
- Mismatched pairings (e.g., writing live – blue).
Alternating vs Direct Potential Difference
Describing directional behaviour of a.c. and d.c. [2 Marks]
✅ Correct Answers
- Alternating: continuously changes direction [1 mark]
- Direct: always remains in the same direction (one direction only) [1 mark]
❌ Common Errors
- Vague terms like "a.c. moves up and down" or "d.c. is a straight flat line" without mentioning direction.
- Confusing direction with magnitude (e.g., saying "d.c. stays at the same voltage"). Even if d.c. fluctuates in size, it is still direct if it does not change direction.
🧠 Examiner Commentary
Always use the word direction. Mentioning that alternating current/p.d. reverses or alternates continuously, whereas direct current/p.d. flows/acts in one direction only, gets full marks every time.
Charging Rate While in Use
Explaining power division and charging times [2 Marks]
✅ Correct Answers
- Energy or power is transferred / used by the laptop screen and components (when in use) [1 mark]
- Therefore, the power delivered to the battery is reduced / the rate of energy transfer to the battery is lower [1 mark]
🧠 Exam Technique: Power Sharing
Think of charger power as a fixed flow of water:
- Total Power = Power to run laptop + Power to charge battery
- If total power is fixed, any power consumed by the running laptop directly subtracts from the rate of energy entering the battery.
❌ Common Errors
Simply stating "the laptop is on so it takes longer" just repeats the question stem without explaining the split in energy transfer or reduced power to the battery.
Full Charging Time Calculation
Multi-step calculation involving power, energy, and unit conversions [6 Marks]
📐 Step-by-Step Calculation
- Calculate the power used by the laptop:
Formula: P = V × I
P = 15 V × 4.8 A = 72 W[2 marks awarded: 1 for working, 1 for 72 W] - Calculate the net power available to charge the battery:
Charger supplies 97 W; laptop uses 72 W.
ΔP = 97 - 72 = 25 W[1 mark awarded] - Convert battery energy capacity to standard SI units (Joules):
E = 225 kJ = 225 × 1000 = 225 000 J - Substitute into power-energy equation:
Formula: Power = Energy ÷ time → 25 = 225 000 / t[1 mark awarded] - Calculate time in seconds:
t = 225 000 / 25 = 9 000 s[1 mark awarded] - Convert seconds into hours:
1 hour = 60 × 60 = 3600 seconds.
t = 9 000 ÷ 3 600 = 2.5 hours[1 mark awarded]
❌ Common Calculation Traps
- Trap 1 (Unit conversion): Forgetting to multiply 225 kJ by 1000 to get Joules.
- Trap 2 (Time conversion): Dividing by 60 instead of 3600 (converting to minutes instead of hours).
- Trap 3 (Wrong power): Using 97 W or 72 W in the time equation instead of finding the difference ( 25 W ).
🧠 Examiner Commentary
This is an extended 6-mark calculation that rewards structured, tidy working. Even if an arithmetic error occurs mid-way, error-carried-forward (ecf) marks can be awarded if your formula substitutions and conversion steps are clear.
Topics
Physics · P1: Energy · P2: Electricity
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 1 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.