# A student notices that their home has two types of lighting: old incandescent bulbs and newer LED bulbs. Both types produce the same amount of light, but the LED bulbs have a much lower power-rating. Explain what is meant by the term power-rating and explain why using LED bulbs instead of incandescent bulbs reduces the cost of the electricity bill.

> WJEC GCSE Physics (Wales) — 1.4 Domestic electricity · Explain · 4 marks

> An incandescent bulb has a power-rating of 60 W. An LED bulb produces the same amount of light but has a power-rating of only 8 W.

## Mark scheme (4 marks)

1. Power-rating is the maximum rate of energy transfer of an appliance
2. The LED bulb transfers energy at a lower rate than the incandescent bulb (for the same light output)
3. The incandescent bulb produces more waste energy transfer (e.g. heat/thermal energy) than the LED
4. Because the LED uses less energy (per unit time / in total), fewer kilowatt-hours are used, so the electricity bill is lower

## Key terms

- [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-student-notices-that-their-home-1de970d6) · Published by Druglandscape Ltd.