# A student is building a simple electromagnet for a school project. She wraps copper wire around an iron nail and connects the wire to a battery. Explain how the electromagnet works and describe two ways the student could increase the strength of the magnetic field it produces.

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

> An electromagnet consists of a solenoid with an iron core. The student notices that the iron nail attracts small steel paper clips when the circuit is complete, but the paper clips fall off when the circuit is broken.

## Mark scheme (5 marks)

1. When current flows through the wire, a magnetic field is generated around it.
2. Coiling the wire into a solenoid causes the individual magnetic fields to combine/align, producing a stronger, uniform magnetic field.
3. The iron core becomes an induced magnet, strengthening the overall magnetic field.
4. First valid method to increase field strength — increase the current through the wire.
5. Second valid method to increase field strength — increase the number of turns/coils of wire.

## Key terms

- [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 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-is-building-a-simple-3238c99d) · Published by Druglandscape Ltd.