Describe how electricity generated by wind turbines reaches homes, including the role of transformers in the National Grid.

OCR GCSE Physics A: Gateway Science (J249) — P6.1 Energy resources · Describe · 4 marks · View as Markdown

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

A wind farm is built in a remote area of Scotland. The electricity it generates must be transported hundreds of kilometres to homes in cities.

Model answer (4 marks)

Electricity generated by the wind turbines is first stepped up to a high voltage by a step‑up transformer.
The high‑voltage electricity is then transmitted over long‑distance power cables.
Because the voltage is high, the current is low, which minimises the I²R losses in the cables.
Near the consumer a step‑down transformer reduces the voltage to a safe, low level for domestic use.

Examiner tips

Use the word ‘step‑up’ and ‘step‑down’ transformers. Mention high voltage and low current for transmission. Explain why high voltage reduces losses. Show the flow: wind farm → step‑up → transmission → step‑down → home.

Common mistakes

Confusing the direction of voltage change (step‑up vs step‑down). Forgetting to mention that high voltage reduces current and losses. Using vague terms like ‘transmission’ without linking to transformers.

Mark scheme (4 marks)

Electricity is transported along power cables at very high voltage (and low current)
A step-up transformer increases the potential difference (voltage) from the wind farm before transmission
Transmitting at high voltage reduces the current, which reduces the energy lost as heat in the power cables
A step-down transformer reduces the potential difference to a safer, lower voltage for domestic use

Key terms in this question

National Grid