# A student is building an electromagnet for a school project. They wind a coil of wire around an iron core and connect it to a power supply. Explain how the strength of the magnetic field produced by the electromagnet can be increased, and why using an iron core rather than leaving the centre empty makes the electromagnet stronger.

> OCR A-Level Physics A (H556) — 4.4 Waves · Explain · 5 marks

> An electromagnet consists of a solenoid with an iron core. When current flows through the coil, a magnetic field is generated.

## Mark scheme (5 marks)

1. Increasing the current increases the strength of the magnetic field
2. Increasing the number of turns/coils on the solenoid increases the strength of the magnetic field
3. The iron core increases the strength of the magnetic field
4. The iron core becomes an induced magnet / the domains in the iron align with the field
5. The induced magnetism in the iron core is lost when the current is switched off, which is why iron (not steel) is used

## Key terms

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

## 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-student-is-building-an-electromagnet-b5dcbf35) · Published by Druglandscape Ltd.