A wind farm is connected to the National Grid. Describe how electricity generated by the wind farm is made suitable for transmission through power cables across the National Grid, and explain why this process is necessary.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A wind farm uses a transformer to step up the voltage of the electricity it generates.
The higher voltage means the current required to transmit the same power is lower.
Because power loss in the cables is proportional to the square of the current (P_loss = I²R), a lower current reduces the energy lost as heat, making transmission more efficient.
At the receiving end a step‑down transformer reduces the voltage to a safe level for domestic use.
The higher voltage means the current required to transmit the same power is lower.
Because power loss in the cables is proportional to the square of the current (P_loss = I²R), a lower current reduces the energy lost as heat, making transmission more efficient.
At the receiving end a step‑down transformer reduces the voltage to a safe level for domestic use.
Examiner tips
- Use the term ‘step‑up transformer’ and ‘step‑down transformer’ explicitly.
- Show the relationship between voltage, current and power loss (I²R) to justify efficiency.
- Keep the answer concise – 4 marks, so one sentence per point is sufficient.
- Mention the National Grid only if it helps explain the context.
Common mistakes
- Confusing voltage with current – students sometimes say ‘increase current’ instead of ‘increase voltage’.
- Omitting the step‑down transformer at the end of the transmission chain.
- Failing to explain why lower current reduces energy loss (missing the I²R point).
Mark scheme (4 marks)
- A transformer is used to increase (step up) the voltage of the electricity from the wind farm.
- Increasing the voltage reduces the current in the power cables.
- A lower current reduces the energy loss (as heat) in the power cables, making transmission more efficient.
- A step-down transformer is used at the end of transmission to reduce the voltage to a safe level for domestic/household use.
Key terms in this question
Related
- All Eduqas GCSE Physics revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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