# A student wraps a length of insulated wire into a coil around an iron rod and connects it to a battery. The student notices that the iron rod can now pick up steel paperclips. The student then increases the number of turns of wire on the coil. Explain why the iron rod behaves like a magnet, and describe two changes the student could make, other than increasing the number of turns, to make the electromagnet stronger.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.5 Quantum physics · Explain · 5 marks

> An electromagnet is made by wrapping insulated wire around an iron rod and connecting the wire to a battery.

## Mark scheme (5 marks)

1. Current flowing through the wire/coil produces a magnetic field around the wire
2. The iron rod becomes an induced magnet / the iron core increases the strength of the magnetic field
3. The solenoid (coil) produces a magnetic field similar to a bar magnet / the coiled wire causes fields to align and combine into a single stronger field
4. First valid change to increase strength: increase the current (supplied by the battery)
5. Second valid change to increase strength: increase the length of the coil / increase the cross-sectional area of the coil / use a different (more suitable) core material

## Key terms

- [electromagnet](https://www.gradenine.co.uk/glossary/electromagnet)

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](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-length-of-48719173) · Published by Druglandscape Ltd.