# A student investigates the magnetic field produced by a current-carrying wire. She increases the current through the wire and also moves the wire closer to a plotting compass. Explain how the strength of the magnetic field around the wire changes in each case, and describe what effect this has on the deflection of the plotting compass needle.

> Edexcel A-Level Physics (9PH0) — 12.1 Newtonian gravity · Explain · 5 marks

> A plotting compass is placed near a straight wire connected to a power supply. The student changes two variables separately: the size of the current in the wire and the distance between the wire and the compass.

## Mark scheme (5 marks)

1. Increasing the current increases the strength of the magnetic field around the wire
2. A stronger magnetic field causes a greater deflection of the compass needle
3. Moving the wire closer to the compass decreases the distance between the wire and the compass
4. Moving the wire closer therefore causes a greater deflection of the compass needle
5. The plotting compass needle aligns with / shows the direction of the magnetic field produced by the current in the wire

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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-investigates-the-magnetic-field-ddc6f53a) · Published by Druglandscape Ltd.