# A student wraps a long wire into a coil and connects it to a battery to create a solenoid. The student then wants to make the solenoid as strong a magnet as possible. Describe four factors the student could change to increase the strength of the magnetic field produced by the solenoid, and explain why inserting an iron core further increases the field strength.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.4 Waves · Describe · 5 marks

> A solenoid is a wire wrapped into the shape of a coil. When current flows through it, the resulting magnetic field is similar in shape to that of a bar magnet. The strength of this field can be altered in several ways.

## Mark scheme (5 marks)

1. Increase the size (magnitude) of the current through the coil
2. Increase the number of turns (coils) of wire
3. Any one of: increase the cross-sectional area of the coil OR increase the length of the coil (1 mark for either)
4. Iron is easier for magnetic field lines to pass through than air, so inserting an iron core concentrates / strengthens the magnetic field inside the solenoid
5. The iron core becomes an induced magnet (it is magnetised by the solenoid's field), adding to the overall magnetic field strength

## Key terms

- [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 B: Advancing Physics (H557)](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-wraps-a-long-wire-5837e64a) · Published by Druglandscape Ltd.