# An engineer is designing a system to lift scrap iron in a recycling plant using an electromagnet attached to a crane. Describe how the electromagnet is constructed and explain how its magnetic field strength can be increased to lift heavier loads.

> OCR A-Level Physics B: Advancing Physics (H557) — 4.4 Waves · Describe and Explain · 5 marks

> An electromagnet is used in recycling plants to sort and lift magnetic materials. The strength of the electromagnet must be controllable so that loads of different masses can be lifted and released on demand.

## Mark scheme (5 marks)

1. An electromagnet is a solenoid (a coil of wire) with an iron core
2. Current flowing through the wire creates a magnetic field (around the wire / in the solenoid)
3. Increasing the current increases the strength of the magnetic field
4. Increasing the number of turns (coils) on the solenoid increases the magnetic field strength
5. The iron core increases the field strength because it is easier for magnetic field lines to pass through iron than air / iron becomes an induced magnet, adding to the overall field

## 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 B: Advancing Physics (H557)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/an-engineer-is-designing-a-system-153d19ab) · Published by Druglandscape Ltd.