# A generator in a power station produces an alternating current. State what is meant by alternating current and explain why alternating current, rather than direct current, cannot be used to operate an electromagnet that is required to repeatedly lift and release magnetic materials.

> Cambridge International IGCSE Physics (0625) — 4.5 Electromagnetic effects · State and Explain · 4 marks

## Mark scheme (4 marks)

1. Alternating current is a current in which electrons change direction of flow regularly / periodically
2. An electromagnet requires direct current / a current in one direction to maintain a consistent magnetic field / polarity
3. With a.c., the magnetic poles of the electromagnet reverse repeatedly, so the force on the magnetic material alternates between attraction and repulsion
4. Therefore the electromagnet could not hold / lift the magnetic material reliably / consistently

## Key terms

- [alternating current](https://www.gradenine.co.uk/glossary/alternating-current)
- [direct current](https://www.gradenine.co.uk/glossary/direct-current)
- [electromagnet](https://www.gradenine.co.uk/glossary/electromagnet)
- [magnetic materials](https://www.gradenine.co.uk/glossary/magnetic-materials)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](https://www.gradenine.co.uk/learn)
- [How to answer "State and 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/a-generator-in-a-power-station-24c15b8f) · Published by Druglandscape Ltd.