# A food blender is used in a kitchen to blend ingredients. The blender transfers electrical energy, but not all of this energy is a useful energy transfer. Explain how energy is wasted in the blender and describe two ways in which the efficiency of the blender could be improved.

> OCR GCSE Physics A: Gateway Science (J249) — P5.2 Power and efficiency · Explain · 4 marks

> A food blender transfers electrical energy. Its motor spins at high speed, but the blender becomes warm and noisy during use.

## Mark scheme (4 marks)

1. Energy is wasted as heat (thermal energy) due to the resistance of the wires / motor heating up
2. Energy is also wasted as sound (noise produced by the spinning blades/motor)
3. Lubrication of the moving parts reduces friction, reducing heat loss and improving efficiency
4. Reducing the current through the motor decreases power loss in the wires (since power loss = I²R), reducing waste heat and improving efficiency

## Key terms

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

## 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-food-blender-is-used-in-a317474b) · Published by Druglandscape Ltd.