# A student builds an electric motor using a coil of wire placed between two permanent magnets. When current flows through the coil, it begins to rotate. Explain how the electric motor produces rotation.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.3 Electrical circuits · Explain · 5 marks

> An electric motor consists of a current-carrying coil of wire positioned between the poles of two permanent magnets. The two sides of the coil that are perpendicular to the magnetic field experience forces, causing the coil to rotate continuously.

## Mark scheme (5 marks)

1. The current-carrying coil produces a magnetic field (around it)
2. The magnetic field of the coil interacts with the magnetic field of the permanent magnets
3. The two sides of the coil perpendicular to the magnetic field experience forces in opposite directions
4. Fleming's left-hand rule can be used to determine the direction of the force on each side of the coil
5. The opposing forces on the two sides cause the coil to rotate (about its axis)

## Key terms

- [electric motor](https://www.gradenine.co.uk/glossary/electric-motor)
- [permanent magnet](https://www.gradenine.co.uk/glossary/permanent-magnet)

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](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/a-student-builds-an-electric-motor-6bc807df) · Published by Druglandscape Ltd.