# A student sets up an electromagnet by wrapping a wire into a coil and connecting it to a power supply. The student wants to make the electromagnet as strong as possible. Describe four factors the student could change to increase the strength of the magnetic field produced by the electromagnet, and explain why inserting an iron core into the centre of the coil increases the field strength.

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

> An electromagnet is a solenoid with an iron core. The strength of the magnetic field it produces depends on several factors.

## Mark scheme (5 marks)

1. Increase the current (flowing through the coil) to increase field strength
2. Increase the number of turns/coils on the solenoid
3. Any one of: increase the length of the coil / increase the cross-sectional area of the coil
4. The iron core is easier for magnetic field lines to pass through than air, so the field is concentrated/strengthened inside the coil
5. The iron core becomes an induced magnet, aligning with the existing field and reinforcing/adding to the overall magnetic field of the solenoid

## 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 A (H556)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-sets-up-an-electromagnet-1f4a31fb) · Published by Druglandscape Ltd.