# A student wraps a wire into a solenoid and connects it to a variable power supply. She places a soft iron core inside the solenoid to create an electromagnet. Explain how changing the design of this electromagnet can increase the strength of its magnetic field. Give four different ways.

> Edexcel A-Level Physics (9PH0) — 12.1 Newtonian gravity · Explain · 5 marks

## Mark scheme (5 marks)

1. Increasing the current increases the magnetic field strength
2. Increasing the number of turns / coils of wire increases the magnetic field strength
3. Using a soft iron core (rather than air) increases the magnetic field strength because field lines pass through iron more easily than air / iron is magnetised by induction and adds to the field
4. Decreasing the length of the solenoid (while keeping the number of turns the same) increases field strength / increasing the density of turns per unit length increases the field
5. Increasing the cross-sectional area of the solenoid increases the strength / size of the magnetic field produced

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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-wraps-a-wire-into-143db88e) · Published by Druglandscape Ltd.