# An engineer is designing a scrapyard crane that uses an electromagnet to lift steel beams. Explain how the electromagnet works and describe two changes the engineer could make to increase the strength of the magnetic field it produces.

> OCR A-Level Physics A (H556) — 4.1 Charge and current · Explain · 5 marks

> A scrapyard crane uses an electromagnet consisting of a solenoid with an iron core connected to a power supply. When switched on, the electromagnet can lift heavy steel beams. When switched off, the steel beams are released.

## Mark scheme (5 marks)

1. When current flows through the solenoid (coil of wire), a magnetic field is generated around/inside it
2. The iron core becomes an induced magnet, increasing the overall strength of the magnetic field
3. The steel beams are magnetic materials that become induced magnets, so they are attracted to the electromagnet
4. One valid change to increase field strength, e.g. increase the current / increase the number of turns (coils) on the solenoid / add or use a larger iron core
5. A second distinct valid change to increase field strength, e.g. a different one from: increase the current / increase the number of turns / use a larger cross-sectional area core

## 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/an-engineer-is-designing-a-scrapyard-b089e570) · Published by Druglandscape Ltd.