# A student sets up a solenoid by wrapping wire around a cardboard tube and connecting it to a power supply. The student wants to make the solenoid as strong an electromagnet 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 its strength.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.1 Charge and current · Describe · 5 marks

> A solenoid is a coil of wire that produces a magnetic field similar in shape to that of a bar magnet. An electromagnet is a solenoid with an iron core. Several factors affect the strength of the magnetic field a solenoid produces.

## Mark scheme (5 marks)

1. Increase the current through the wire / size of current
2. Increase the number of turns / coils of wire
3. Any one further correct factor from: increase the cross-sectional area of the coil OR change the core material to one that allows field lines to pass through more easily (accept: use a material with higher magnetic permeability) OR increase the length of the coil
4. Iron core: magnetic field lines pass through iron more easily than through air
5. Iron core: the iron becomes an induced magnet / the iron itself becomes magnetised, adding to the overall magnetic field strength

## Key terms

- [solenoid](https://www.gradenine.co.uk/glossary/solenoid)
- [electromagnet](https://www.gradenine.co.uk/glossary/electromagnet)
- [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-sets-up-a-solenoid-94a40781) · Published by Druglandscape Ltd.