# A technician is investigating a solenoid connected to a battery. She notices that the solenoid attracts a nearby iron nail. She then makes changes to the solenoid to increase the strength of its magnetic field. Describe four factors that could increase the strength of the magnetic field produced by the solenoid, and explain why inserting an iron core into the solenoid makes it an electromagnet.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.3 Electrical circuits · Describe · 5 marks

> A solenoid is a wire wrapped into the shape of a coil. When current flows through it, it produces a strong and uniform magnetic field inside, similar in shape to the field of a bar magnet.

## Mark scheme (5 marks)

1. Any one of: increasing the size of the current through the solenoid increases the magnetic field strength
2. Any second distinct factor from: increasing the number of turns/coils, increasing the length of the coil, or increasing the cross-sectional area of the coil
3. Any third distinct factor from the remaining options (number of turns, length of coil, cross-sectional area, or type of core used)
4. Inserting an iron core means the solenoid becomes an electromagnet / the iron core is an induced magnet that strengthens the field
5. Iron is easier for magnetic field lines to pass through than air, so the magnetic field is strengthened / iron becomes magnetised in the field, adding to the overall field

## 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-technician-is-investigating-a-solenoid-88701058) · Published by Druglandscape Ltd.