# Describe the role of step-up and step-down transformers in the National Grid, and explain why each is necessary.

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

## Mark scheme (4 marks)

1. Step-up transformers increase the potential difference from the power station to the National Grid transmission cables.
2. Increasing the potential difference causes the current to decrease (as power is constant).
3. A lower current means less energy is lost (as heat) in the transmission cables.
4. Step-down transformers decrease the potential difference from the National Grid to a safe, usable level for consumers.

## Key terms

- [step-down transformer](https://www.gradenine.co.uk/glossary/step-down-transformer)
- [National Grid](https://www.gradenine.co.uk/glossary/national-grid)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-role-of-step-up-and-4f755ddf) · Published by Druglandscape Ltd.