AQA GCSE Combined Science: Trilogy Physics Paper 1 (Higher), 2019: Question 3

✅ Correct answer

An energy resource that cannot be replenished as it is used.

Also accepted: a resource that will run out.

💡 Key knowledge

• “Non-renewable” means it is used up faster than it is replaced.
• Examples: petrol, coal, oil, natural gas.
• For 1 mark, a clear definition is enough.

🧠 Exam technique

• Use a short, precise definition.
• Link to the idea of being used up or running out.
• One well-chosen sentence can get full marks.

❌ Common errors

• “It cannot be reused” — this is not the same as non-renewable.
• Giving only an example, like “petrol”, without defining it.
• Writing “it is bad for the environment” — not what the question asks.

📐 Calculation steps

1. Use the power equation: P = IV
2. Convert power: 6.9 kW = 6900 W
3. Substitute values: 6900 = 230 × I
4. Rearrange: I = 6900 ÷ 230
5. Calculate: I = 30 A

✅ Correct answer

Current = 30 A

💡 Key knowledge

• P = IV
• Power is measured in watts (W).
• Potential difference is measured in volts (V).
• Current is measured in amperes (A).

🧠 Exam technique

• Show each step clearly to secure method marks.
• Always convert kW to W before substituting.
• Give the final answer with the correct unit: A .
• The mark scheme allows the answer 30 (A) for full marks.

❌ Common errors

• Forgetting to convert 6.9 kW into 6900 W .
• Using the wrong equation, such as P = V/R .
• Not including the unit A .
• Calculating 6900 ÷ 230 incorrectly.

✅ Correct answer

• Direct potential difference is always in the same direction.
• Alternating potential difference changes direction.

💡 Key knowledge

• DC means the potential difference does not reverse.
• AC means the potential difference repeatedly reverses direction.
• Mains electricity is AC.

🧠 Exam technique

• Make the comparison explicit: direct vs alternating.
• Use “same direction” and “changes direction” for easy marks.
• The mark scheme also accepts “direct current” and “alternating current”.

❌ Common errors

• Saying only “AC is different from DC” without explaining how.
• Mixing up current and potential difference.
• Writing about voltage size instead of direction.

✅ Correct answer

A low resistance cable causes less potential difference to be lost across the cable, so it is more efficient.

Also accepted: lower power/energy dissipation, or it won’t get as hot.

💡 Key knowledge

• Resistance causes energy to be transferred to thermal energy in the cable.
• Lower resistance means less energy is wasted as heat.
• More of the electrical energy reaches the battery.

🧠 Exam technique

• For full marks, give a cause and effect explanation.
• Good wording: “lower resistance gives a greater current for the same potential difference, so the car battery can charge faster.”
• Either efficiency or faster charging can score, but explain clearly.

❌ Common errors

• Only saying “it is better” without saying why.
• Talking about “more electricity” in a vague way.
• Forgetting the link between resistance and heating.
• Confusing resistance with voltage.

Key facts to remember

• Non-renewable = cannot be replenished as it is used, so it will run out.
• Use P = IV for charging calculations.
• 6.9 kW = 6900 W
• DC stays in the same direction; AC changes direction.
• Low resistance cables waste less energy as heat.

Best exam habits

• Write the equation before substituting numbers.
• Always include units.
• Use direct comparison words: same direction, changes direction.
• Explain “why”, not just “what”.