# Explain why electrical power is transmitted across the National Grid at a high potential difference rather than a low potential difference.

> AQA GCSE Physics (8463) — 4.2.5 The National Grid · Explain · 4 marks

## Mark scheme (4 marks)

1. Increasing the potential difference (using a step-up transformer) causes the current to decrease
2. Power loss in the transmission cables is reduced when current is lower
3. This is because power loss is related to (the square of) the current, so a smaller current results in significantly less power lost as heat
4. Step-down transformers are used to reduce the potential difference to safe, usable levels for consumers at the end of the transmission

## Key terms

- [National Grid](https://www.gradenine.co.uk/glossary/national-grid)
- [potential difference](https://www.gradenine.co.uk/glossary/potential-difference)

## Related

- [Revision notes for AQA GCSE Physics (8463)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-electrical-power-is-transmitted-1e2859eb) · Published by Druglandscape Ltd.