A fault occurs in the National Grid and all step-down transformers stop working. Explain what effect this would have on consumers and why this effect occurs.

AQA GCSE Physics (8463) — 4.2.5 The National Grid · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Consumers would receive electrical power at a very high potential difference from the transmission cables. Step‑down transformers normally reduce the potential difference to the safe, usable level of 230 V. Without the transformers the high potential difference would be dangerous and unsafe for consumers. Appliances are designed to operate at 230 V, so the high potential difference would damage them or prevent them from functioning correctly.

Examiner tips

  • Use the term "step‑down transformers" and state their role in reducing voltage.
  • Explain the consequence (dangerous high voltage) and link it to appliance design.
  • Show clear cause‑effect structure: fault → no transformers → high voltage → danger/damage.

Common mistakes

  • Saying the voltage is "low" instead of "high".
  • Forgetting to mention that appliances are designed for 230 V.
  • Using vague words like "problem" instead of specifying the high potential difference and its effects.

Mark scheme (4 marks)

  1. Consumers would receive electrical power at a very high potential difference (from the transmission cables)
  2. Step-down transformers normally decrease/reduce the potential difference to safe, usable levels
  3. The high potential difference would be dangerous / unsafe for consumers
  4. Appliances are designed to operate at 230 V (mains supply), so the high potential difference would damage them / they would not function correctly

Key terms in this question

step-down transformers · National Grid · consumers

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