# Explain why a current-carrying wire placed between the poles of a permanent magnet experiences a force, and describe what happens to the size of this force when the current in the wire is increased.

> AQA A-Level Physics (7408) — 3.7.5 Magnetic Fields · Explain · 5 marks

> A straight wire is connected to a battery and placed horizontally between the north and south poles of a U-shaped permanent magnet so that the wire is at right angles to the magnetic field.

## Mark scheme (5 marks)

1. The current in the wire produces its own magnetic field around the wire
2. The magnetic field of the wire interacts with the magnetic field of the permanent magnet
3. This interaction produces a resultant/combined magnetic field that is not uniform
4. The force on the wire acts at right angles to both the current and the magnetic field (motor effect)
5. Increasing the current increases the size of the force on the wire

## Key terms

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

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-a-current-carrying-wire-placed-34417ee1) · Published by Druglandscape Ltd.