AQA GCSE Combined Science: Trilogy Physics Paper 1 (Foundation), 2022: Question 5

8 marks · Standard Demand difficulty · Short Answer

Analyze UK energy resource usage from a graph, identify carbon-emitting fuels, and explain how step-up transformers improve the efficiency of the National Grid.

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Question

The image shows a line graph (Figure 9) titled 'Electrical power in gigawatts' versus 'Time of day' for one day in 2020. Five lines represent total demand, gas, nuclear, wind, and coal. The demand peaks at approximately 30,000 GW around 6 pm. Below the graph are four questions: 05.1 asks for the percentage of maximum demand generated by gas at 6 pm; 05.2 is a multiple-choice question about reducing carbon emissions; 05.3 asks for the name of the transformer and cable network; and 05.4 asks for an explanation of how step-up transformers increase efficiency.
Question text

05 Figure 9 shows some of the energy resources used to meet the demand for electrical

power in the UK on one day in 2020.

Figure 9

05.1 The maximum demand for electrical power on that day was at 6 pm.

Determine the percentage of the maximum demand for electrical power that was

generated using gas.

[3 marks]

Percentage = %

05.2 The UK government wants to reduce carbon emissions as much as possible.

Which energy resources need to be used less to achieve this?

[1 mark]

Tick ( ) one box.

Coal and gas

Gas and nuclear

Wind and coal

Wind and nuclear 24

A network of transformers and transmission cables transfers electrical power from

power stations to consumers.

05.3 What is this network called?

[1 mark]

05.4 Explain how using step-up transformers makes the network efficient.

*23* [3 marks]

Mark scheme

Show the mark scheme The mark scheme for question 5 provides the following points: 05.1 awards 3 marks for reading 16,500 GW (gas) and 30,000 GW (demand) from the graph and calculating the percentage as 55%. 05.2 awards 1 mark for 'coal and gas'. 05.3 awards 1 mark for 'the national grid'. 05.4 awards 3 marks for explaining that potential difference increases, current is reduced, and therefore there is less energy loss to the surroundings.

Question 5

AO /

Question Answers Extra information Mark

Spec. Ref.

05.1 16 500(GW) and 1 AO3

30 000 (GW) read from graph 6.1.3

16500 allow a correct substitution using 1

percentage = (×100%) a value of 15300 or 18000 for

30000

gas

percentage = 55 (%) allow an answer consistent with 1

a value of 15300 or 18000 for

gas

AO /

Spec. Ref.

05.2 coal and gas 1 AO1.1

6.1.3

AO /

Spec. Ref.

05.3 the national grid 1 AO1

6.2.4.3

AO /

Spec. Ref.

05.4 potential difference increases allow large potential difference 1 AO1

6.2.4.3

current is reduced allow small current 1

so there is less / low energy loss allow less / low heating in the 1

(to the surroundings) transmission cables

ignore resistance

do not allow no energy loss 15

Total Question 5 8

How to answer it

Energy Resources and the National Grid

What this question tests

This question assesses your ability to interpret complex line graphs, calculate percentages from data, identify carbon-emitting energy resources, and explain the physics behind efficient power transmission in the National Grid.

Part (05.1)

Graph Analysis & Percentages

Determine the percentage of maximum demand generated by gas at 6 pm.

📐 Step-by-Step Calculation

  1. Read Demand: Find 6 pm on the x-axis. Follow it up to the 'Demand' line. Value = 30,000 GW.
  2. Read Gas: Follow 6 pm up to the dashed 'Gas' line. Value = 16,500 GW.
  3. Calculate: (Part / Total) × 100
    (16,500 / 30,000) × 100 = 55%

🧠 Exam Technique

Always draw lines on your graph with a ruler to ensure accuracy. On this scale, each small vertical square represents 500 GW. The examiner allowed a small range for the gas reading (15,300 to 18,000), but 16,500 is the most precise reading.

❌ Common Errors

  • Scale Misreading: Thinking each small square is 100 or 1000 instead of 500.
  • Wrong Line: Accidentally reading the 'Nuclear' or 'Wind' line instead of 'Gas'.
Mark breakdown: 1 mark for correct readings, 1 mark for substitution, 1 mark for the final answer.
Part (05.2)

Environmental Impact

Which energy resources need to be used less to reduce carbon emissions?

✅ Correct Answer

Coal and gas

💡 Key Knowledge

Carbon emissions (specifically CO₂) are primarily caused by burning fossil fuels. Coal, oil, and gas are the three main fossil fuels. Nuclear, wind, and solar are considered "low carbon" or "carbon neutral" during operation.

Part (05.3)

The National Grid

What is the network of transformers and cables called?

✅ Correct Answer

The National Grid

🧠 Exam Technique

Be specific. Simply saying "the grid" or "power lines" is often not enough for the mark. Use the full technical term.

Part (05.4)

Efficiency & Transformers

Explain how using step-up transformers makes the network efficient.

💡 The Efficiency Chain

To get full marks here, you must link three logical steps in order:

  1. The step-up transformer increases the potential difference (voltage).
  2. This reduces the current in the transmission cables.
  3. A lower current means less heating/energy loss to the surroundings.

🧠 Examiner Commentary

Top-level responses clearly stated that energy is lost as heat. You must mention that the current is reduced—don't just say the current "changes".

❌ Common Errors

  • "No energy loss": Never say this! Some energy is always lost; we just want to reduce it.
  • Resistance: Students often wrongly say the transformer "reduces resistance". The resistance of the actual wire doesn't change; only the current flowing through it changes.
Mark breakdown: 1 mark for PD increase, 1 mark for current reduction, 1 mark for less energy loss.

Topics

Physics · P1: Energy · P7: Magnetism and Electromagnetism

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 1 (Foundation), 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.