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

💡 Key knowledge

• Read values carefully from the axes and grid lines.
• Wind and nuclear are low-carbon compared with coal and gas.
• The network of cables and transformers is the national grid.
• Step-up transformers increase potential difference and reduce current.

🧠 Exam technique

• For 3-mark calculations: show the value from the graph, the method, and the final answer.
• Always include units in graph answers: GW.
• For explanation questions, use linked physics points: p.d. increases → current reduces → less heating loss.

✅ Correct answer

55%

📐 Calculations: step by step

1. Read the maximum demand from the graph at 6 pm: 30 000 GW.
2. Read the amount generated by gas at 6 pm: 16 500 GW.
3. Use the percentage formula:
   percentage = (16 500 ÷ 30 000) × 100
4. Calculate:
   = 0.55 × 100 = 55%

🧠 How marks are awarded

• 1 mark for reading the correct demand value.
• 1 mark for using the gas value correctly in the calculation.
• 1 mark for the final correct percentage.

Examiner note: credit was given for a correct method even if the graph values were slightly different, as long as they were consistent with the candidate’s own reading.

❌ Common errors

• Using the wrong time on the graph.
• Reading the demand line instead of the gas line.
• Forgetting to multiply by 100.
• Giving 0.55 instead of 55% .

✅ Correct answer

Coal and gas

💡 Key knowledge

• Coal and gas are fossil fuels.
• Burning fossil fuels releases carbon dioxide.
• Wind and nuclear are much lower in carbon emissions during electricity generation.

🧠 Exam technique

This is a simple recall question: choose the options that produce carbon emissions when generating electricity.

❌ Common errors

• Choosing nuclear because it is associated with waste, not carbon emissions.
• Choosing wind because it is not always available, even though it is low carbon.

✅ Correct answer

the national grid

💡 Key knowledge

• The national grid carries electricity from power stations to homes and businesses.
• It uses transformers to change the potential difference for efficient transmission.

❌ Common errors

• Writing only grid instead of the full term.
• Confusing the national grid with a specific power station.

✅ Correct answer

• The step-up transformer increases potential difference.
• This means the current is reduced.
• Because the current is smaller, there is less energy loss as heating in the transmission cables.

💡 Key knowledge

• Energy is lost in cables because they have resistance.
• Lower current means less heating of the cables.
• This makes more of the generated electrical power reach consumers.

🧠 Exam technique

For 3 marks, you need a chain of explanation. A strong answer uses all three ideas:

1. Potential difference increases
2. Current decreases
3. Less energy is lost in the cables

Examiner insight: top-level responses linked the reduced current to reduced heating in the transmission wires. Simply saying “it is more efficient” was not enough.

❌ Common errors

• Saying the transformer “creates more energy” — it does not.
• Writing “no energy is lost” — incorrect.
• Talking only about resistance without explaining the effect on current and heating.

01.1

55%

01.2

coal and gas

01.3

the national grid

01.4

Potential difference increases, current decreases, so there is less energy loss as heat in the cables.