# A solenoid is used as an electromagnet to pick up iron components on a production line. An engineer wants to make the electromagnet stronger. Explain three factors the engineer could change to increase the strength of the magnetic field produced by the solenoid, and for each factor state how it should be changed.

> OCR A-Level Physics A (H556) — 4.1 Charge and current · Explain · 5 marks

> A solenoid consists of a coil of wire wound around an iron core. When current flows through the wire, a strong magnetic field is produced inside the coil.

## Mark scheme (5 marks)

1. Increase the number of turns (coils) of wire on the solenoid — more turns means a stronger magnetic field
2. Increase the current flowing through the wire — a greater current produces a stronger magnetic field
3. Use an iron core (instead of air) — iron is easier for magnetic field lines to pass through than air, increasing field strength
4. Any correct fourth factor clearly stated with correct directional change: increase the cross-sectional area of the solenoid OR increase the length of the coil — award 1 mark for a correct additional factor with correct change stated
5. A clear and accurate explanation is given for at least two of the factors chosen — e.g. more turns causes the individual magnetic fields around each loop to combine/align, producing a larger overall field; or greater current produces a stronger field because the magnetic field strength around a wire depends on the magnitude of the current

## Key terms

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

## Related

- [Revision notes for OCR A-Level Physics A (H556)](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-solenoid-is-used-as-an-caa96e62) · Published by Druglandscape Ltd.