# When a current-carrying wire is placed in a magnetic field, it can experience a force. Explain why reversing the direction of the current in the wire causes the direction of this force to reverse.

> WJEC GCSE Physics (Wales) — 2.5 Magnetism and electromagnetism · Explain · 4 marks

> An engineer is testing a simple electric motor. She notices that when she reverses the current supplied to a wire held between the poles of a magnet, the wire moves in the opposite direction to before.

## Mark scheme (4 marks)

1. The force on the wire is produced by the interaction between the magnetic field of the magnet and the magnetic field created by the current in the wire.
2. Reversing the current reverses the direction of the magnetic field produced by the wire.
3. The interaction between the reversed wire field and the magnet's field now acts in the opposite sense.
4. This reversed interaction produces a force on the wire in the opposite direction.

## Key terms

- [current](https://www.gradenine.co.uk/glossary/current)
- [magnetic field](https://www.gradenine.co.uk/glossary/magnetic-field)
- [force](https://www.gradenine.co.uk/glossary/force)

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](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/when-a-current-carrying-wire-is-placed-5ca7f9bd) · Published by Druglandscape Ltd.