# A solenoid is used to lift steel paper clips in a factory sorting machine. An engineer wants to make the solenoid's magnetic field as strong as possible. Describe four factors that affect the strength of the magnetic field produced by a solenoid, and explain why inserting an iron core into the solenoid increases its strength.

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

> A factory uses a solenoid to sort and lift small steel components along a production line. The engineer in charge wants to maximise the lifting force of the solenoid.

## Mark scheme (5 marks)

1. Any one correct factor affecting solenoid field strength: size of current / number of turns (coils) / length of coil / cross-sectional area / type of core used
2. A second correct and distinct factor from the list above
3. A third correct and distinct factor from the list above
4. A fourth correct and distinct factor from the list above
5. Iron core increases strength because magnetic field lines pass through iron more easily than through air (accept: iron becomes an induced magnet / iron concentrates / strengthens the field inside the solenoid)

## Key terms

- [solenoid](https://www.gradenine.co.uk/glossary/solenoid)
- [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 A (H556)](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-solenoid-is-used-to-lift-5699cdb6) · Published by Druglandscape Ltd.