# A student sets up an electromagnet by wrapping wire around an iron core and connecting it to a power supply. The student wants to use the electromagnet to pick up as many steel paperclips as possible. Explain how the student could increase the strength of the magnetic field produced by the electromagnet, and why the paperclips are attracted to the electromagnet.

> OCR A-Level Physics A (H556) — 4.2 Energy, power and resistance · Explain · 5 marks

> An electromagnet is made from a solenoid with an iron core. The solenoid is connected to a variable power supply so the current can be changed.

## Mark scheme (5 marks)

1. Increasing the current increases the strength of the magnetic field
2. Increasing the number of turns/coils of wire increases the strength of the magnetic field
3. The iron core increases the strength of the magnetic field / it is easier for field lines to pass through iron than air
4. The paperclips are induced magnets / they become magnetised when placed in the magnetic field of the electromagnet
5. Induced magnetism always produces an attractive force / the paperclips are attracted to the electromagnet

## 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 "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-sets-up-an-electromagnet-a2a4b843) · Published by Druglandscape Ltd.