# A factory uses a large electric motor to drive a conveyor belt. The motor has a power rating of 500 W. During operation, the motor gets warm and produces a humming sound. Explain how these observations show that the motor is not perfectly efficient, and describe one way the efficiency of the motor could be improved.

> OCR GCSE Physics A: Gateway Science (J249) — P7 Energy · Explain · 4 marks

> Electric motors are used widely in industry. Like all real machines, they transfer some energy in ways that do not directly serve their purpose.

## Mark scheme (4 marks)

1. The heat produced by the motor is a waste energy transfer (energy transferred to a form that does not directly serve the purpose of the system).
2. The sound produced by the motor is also a waste energy transfer (energy transferred to a form that does not directly serve the purpose of the system).
3. Because energy is transferred as heat and sound rather than entirely as useful kinetic energy / mechanical energy, the useful output is less than the total input, so efficiency is less than 1 (or 100%).
4. Efficiency could be improved by lubricating the moving parts of the motor to reduce friction, thereby reducing the waste heat energy transfer.

## Key terms

- [efficiency](https://www.gradenine.co.uk/glossary/efficiency)
- [power rating](https://www.gradenine.co.uk/glossary/power-rating)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](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-factory-uses-a-large-electric-9fe46ff2) · Published by Druglandscape Ltd.