# A security system uses an electromagnet to hold a heavy door shut. The electromagnet is made from a solenoid with an iron core. Explain how the electromagnet produces a magnetic field and describe three ways the engineer could increase the strength of this magnetic field.

> OCR A-Level Physics A (H556) — 4.5 Quantum physics · Explain · 5 marks

> An electromagnet in a door-locking system consists of a coil of insulated wire wound around an iron core, connected to a direct current power supply.

## Mark scheme (5 marks)

1. Current flowing through the solenoid (coil of wire) produces a magnetic field
2. The iron core increases the strength of the magnetic field because field lines pass through iron more easily than air
3. Increase the number of turns/coils of wire on the solenoid
4. Increase the current flowing through the coil
5. Any one further valid method: use a core material that is more easily magnetised / increase the cross-sectional area of the coil

## Key terms

- [electromagnet](https://www.gradenine.co.uk/glossary/electromagnet)
- [solenoid](https://www.gradenine.co.uk/glossary/solenoid)
- [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-security-system-uses-an-electromagnet-b6a04a55) · Published by Druglandscape Ltd.