AQA GCSE Combined Science: Trilogy Physics Paper 1 (Foundation), November 2020: Question 3

✅ Correct Answer

Tick the first box:

☑ It can be replenished as it is used.

💡 Key Knowledge

A renewable energy resource is one that is replenished at a faster rate than, or the same rate as, it is used up. Therefore, it will not run out.

❌ Common Errors

• Confusing "renewable" with "clean" or "green" (e.g. picking "It produces no greenhouse gases"). Biomass is renewable, yet burning it releases CO₂!
• Stating "it can be reused" — energy itself cannot be reused; resources are replenished.

💡 Key Knowledge

• Biomass: Trees and crops can be grown continuously to replace those burned (renewable).
• Nuclear: Uses uranium or plutonium fuel rods, which are finite mined mineral fuels (non-renewable).
• Natural gas: A fossil fuel formed over millions of years (non-renewable).

❌ Common Misconception

Many students incorrectly mark nuclear as renewable because it does not produce greenhouse gases during electricity generation. Nuclear is non-renewable because radioactive ores in the Earth's crust are finite.

✅ Correct Answer

• When the wind turbine spins faster there is an increase in its kinetic energy.
• Charging the battery increases the chemical store of energy of the battery.

🧠 Exam Technique

Notice the exact phrase: "store of energy of the battery". Batteries do not store "electrical energy" — electricity is an energy transfer pathway (current). Energy in batteries is always stored chemically.

✅ Correct Answer (Select Two)

• ☑ Less energy is needed to heat the house.
• ☑ The roof is a better insulator.

💡 Key Knowledge

Thermal conductivity is a measure of how quickly energy transfers through a material via conduction.

• Lower thermal conductivity = slower rate of heat loss = better insulator.
• Because heat escapes much more slowly, the heating system does not need to run as much, meaning less energy is needed to keep the house warm.

❌ Common Errors

Counting zeros incorrectly! Students often write 78 000 or 7 800 000 . Always double check your multiplication on your calculator.

🧠 Exam Tip

Writing down the substitution step ( 26 000 × 30 ) guarantees 1 method mark, even if you make a typing error on the final answer.

✅ Correct Answer

efficiency = useful power output / total power input

(Useful power out divided by total power in)

🧠 Memory Aid

Remember: "Useful on top". Efficiency can never be greater than 1 (or 100%), so the smaller number (useful output) is always divided by the larger number (total input).

❌ Common Errors

• Dividing instead of multiplying: Doing 26 000 / 0.15 = 173 333 W . This gives an output much larger than the input, which is physically impossible!
• Dividing by 100 unnecessarily when efficiency is already given as a decimal ( 0.15 , not 15% ).

🧠 Sanity Check

The useful output must always be less than the total input (26 000 W). If your answer is bigger than 26 000 W, check your rearrangement immediately!

🧠 Exam Technique

Always give a cause and effect when asked to "explain why it is a good idea":

• Cause: Solar doesn't work at night; wind turbines don't work without wind.
• Effect: Having both provides a more continuous/reliable supply of electricity.

❌ Common Errors

Vague answers like "because it is eco-friendly" or "to get more power" without explaining the complementary nature of solar and wind resources will not secure full marks.