# A student investigates the strength of a solenoid by testing how many small iron paperclips it can hold. The student wants to make the solenoid as strong as possible. Describe four factors the student could change to increase the strength of the magnetic field produced by the solenoid, and explain why adding an iron core increases the field strength.

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

> A student wraps insulated wire around a cardboard tube, connects it to a battery, and uses the solenoid to pick up small iron paperclips. The student notices that changing certain features of the solenoid affects how many paperclips it can hold.

## Mark scheme (5 marks)

1. Increase the number of turns (coils) of wire on the solenoid
2. Increase the size (magnitude) of the current flowing through the solenoid
3. Any one of: decrease the length of the coil (so turns are more concentrated) OR increase the cross-sectional area of the coil
4. An iron core allows magnetic field lines to pass through it more easily than air / concentrates the field lines inside the solenoid
5. The iron core becomes an induced magnet, adding its own magnetic field to that of the solenoid, increasing the overall field strength

## Key terms

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

## 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-investigates-the-strength-of-f3b77c1f) · Published by Druglandscape Ltd.