# A electric kettle has a power-rating of 3 kW. When it is used, some energy is usefully transferred to heat the water, but some energy is wasted. Explain what is meant by useful energy transfer and waste energy transfer in this context, and describe one way in which the efficiency of the kettle could be improved.

> WJEC GCSE Physics (Wales) — 1.3 Making use of energy · Explain · 4 marks

## Mark scheme (4 marks)

1. Useful energy transfer is the transfer of energy that directly serves the purpose of the kettle, i.e. heating the water
2. Waste energy transfer is the transfer of energy to a form that does not directly serve the purpose of the kettle, e.g. heating the surroundings / sound
3. Correct method to improve efficiency stated, e.g. adding thermal insulation to the kettle body / lid
4. Correct explanation of why the method improves efficiency, i.e. it reduces waste energy transfer so a greater proportion of the input energy is usefully transferred

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](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-electric-kettle-has-a-power-rating-740b5a19) · Published by Druglandscape Ltd.