AQA GCSE Physics Physics Paper 1 (Foundation), November 2021: Question 2
12 marks · Standard Demand difficulty · Short Answer
Calculate charge flow, power, energy transfers, and identify national grid components from diagrams and data tables.
Practise this questionQuestion
Question text
02 Figure 2 shows part of the National Grid linking a power station to consumers.
Figure 2
02.1 Name the parts of Figure 2 labelled A and B.
[2 marks]
A
B
02.2 Electricity is transmitted through A at a very high potential difference.
What is the advantage of transmitting electricity at a very high potential difference?
[1 mark]
Tick ( ) one box.
A high potential difference is safer for consumers.
Less thermal energy is transferred to the surroundings.
Power transmission is faster. 7
02.3 The power station generates electricity at a potential difference of 25 000 V.
The energy transferred by the power station in one second is 500 000 000 J.
Calculate the charge flow from the power station in one second.
*06* Use the equation:
energy
charge flow =
potential difference
[2 marks]
Charge flow in one second = C
The electricity supply to a house has a potential difference of 230 V.
Table 1 shows the current in some appliances in the house.
Table 1
Appliance Current in amps
Dishwasher 6.50
DVD player 0.10
Lamp 0.40
TV 0.20
02.4 Calculate the total power of all the appliances in Table 1.
Use the equation:
power = potential difference × current
[3 marks]
Total power = W
02.5 Each appliance in Table 1 is switched on for 2 hours.
Which appliance will transfer the most energy?
Give a reason for your answer.
[2 marks]
Appliance
Reason
02.6 The average energy transferred from the National Grid every second for each person
in the UK is 600 J.
There are 32 000 000 seconds in one year.
Calculate the average energy transferred each year from the National Grid for each
person in the UK.
[2 marks]
Average energy transferred = J
Mark scheme
Show the mark scheme
Question 2
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 A: transmission / power cables allow transmission / power lines 1 AO1
allow cables 4.2.4.3
ignore wires
B: step-down transformer 1
02.2 less thermal energy is 1 AO1
transferred to the surroundings. 4.2.4.3
500 000 000
02.3 charge flow = 1 AO2
25 000 4.2.4.2
charge flow = 20 000 (C) 1
02.4 total current = 7.20 (A) 1 AO2
4.2.4.1
P = 230 × 7.20 allow a correct substitution of an 1
incorrect total current
P = 1656 (W) allow a correct calculation using 1
an incorrect total current
02.5 dishwasher 1 AO3
4.2.4.1
4.2.4.2
has the largest current 1
or
has the largest power (input)
02.6 E = 600 × 32 000 000 1 AO2
4.1.1.4
E = 19 200 000 000 (J) 1
or
E = 1.92 × 1010 (J)
Total 12
How to answer it
National Grid and Domestic Electricity
What this question tests
This question assesses your understanding of the National Grid components, why high potential difference is used during power transmission, and your ability to apply core electrical equations involving charge, power, energy, potential difference, and current.
Naming Key Hardware
✅ Correct Answers
- A: Transmission / power cables (allow lines / cables; ignore 'wires')
- B: Step-down transformer
💡 Key Knowledge
The National Grid uses step-up transformers to increase voltage before transmission, overhead cables to transport electricity across the country, and step-down transformers to reduce voltage safely before it reaches homes.
Advantages of High Voltage
✅ Correct Answers
- Tick: Less thermal energy is transferred to the surroundings.
💡 Key Knowledge
By increasing the potential difference, the current flowing through the transmission cables decreases for the same amount of transferred power ($P = I \times V$). Because energy loss due to resistance is calculated using $E = I² \times R \times t$, a smaller current drastically reduces thermal energy wasted to the environment.
Charge Calculation
📐 Step-by-Step Calculation
- Identify equation: charge flow = energy / potential difference
- Substitute values: charge flow = 500,000,000 / 25,000
- Calculate result: 20,000 C
🧠 Exam Technique
Always double-check your zeroes when copying large numbers from the prompt. Ensure your final answer includes the correct unit (Coulombs or C) if it is not already provided on the answer line.
Multiple Appliances in Parallel
📐 Step-by-Step Calculation
- Find total current: 6.50 + 0.10 + 0.40 + 0.20 = 7.20 A
- Select formula: power = potential difference × current ($P = V \times I$)
- Substitute values: P = 230 × 7.20
- Final Answer: P = 1656 W
❌ Common Errors
Students often forget to add up all the individual currents from Table 1 before multiplying by the UK mains voltage (230 V). If you make an arithmetic error adding the currents, the mark scheme allows ecf (error carried forward) for a correct subsequent multiplication.
Appliance Analysis
✅ Correct Answers
- Appliance: Dishwasher
- Reason: It has the largest current OR the largest power input.
💡 Key Knowledge
Energy transferred depends on power and time ($E = P \times t$). Since all appliances are switched on for the same duration (2 hours), the appliance that draws the highest current—and therefore has the highest power—will transfer the most energy.
Large Scale Energy Calculation
📐 Step-by-Step Calculation
- Identify relationship: Energy per second × seconds in a year
- Substitute values: E = 600 × 32,000,000
- Calculate result: 19,200,000,000 J (or 1.92 × 10¹⁰ J )
🧠 Exam Technique
Standard form is accepted and encouraged for very large numbers. Writing 1.92 × 10¹⁰ J reduces the risk of miscounting trailing zeroes!
Topics
Physics · P1: Energy · P2: Electricity · P7: Magnetism and Electromagnetism
Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Foundation), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.