A hydroelectric power station and a nuclear power station both generate electricity. Describe the process by which each type of power station generates electricity, and state whether each energy resource is renewable or non-renewable.

OCR GCSE Physics A: Gateway Science (J249) — P6.2 Producing electricity · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A government energy adviser is comparing different methods of electricity generation to decide which power stations to build in a mountainous region that also has large uranium reserves.

Model answer (4 marks)

In a hydroelectric power station water is released from a reservoir at height. The gravitational potential energy of the falling water is converted to kinetic energy, which drives a turbine that is connected to a generator.

Hydroelectricity is a renewable energy resource.

In a nuclear power station the nuclear fuel (usually uranium) undergoes fission. The fission reaction releases a large amount of thermal energy, which is used to heat water in a closed loop. The hot water produces steam that drives a turbine connected to a generator.

Nuclear fuel is a non‑renewable energy resource.

Examiner tips

  • Use the word ‘hydroelectric’ and ‘nuclear’ to label each part clearly. Include the key step of water falling or steam driving a turbine. State the renewable/non‑renewable status at the end of each description. Keep the answer concise – 4 marks only.
  • Use the exact wording from the mark scheme where possible (e.g. ‘gravitational potential energy’, ‘fission’, ‘thermal energy’).

Common mistakes

  • Confusing the order of steps (e.g. saying the turbine turns before the water falls). Forgetting to state whether the resource is renewable or not. Using vague terms like ‘energy’ instead of specifying ‘fission’ or ‘gravitational potential energy’.

Mark scheme (4 marks)

  1. In a hydroelectric power station, water moves from a height (using gravitational potential energy) to directly turn turbines.
  2. Hydroelectricity is a renewable energy resource.
  3. In a nuclear power station, fission of nuclear fuel releases thermal energy, which is used to heat water to produce steam that turns turbines.
  4. Nuclear fuel is a non-renewable energy resource.

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