# A student rubs a plastic ruler with a dry cloth. The ruler becomes negatively charged. Explain why the ruler becomes negatively charged and describe what charge, if any, remains on the cloth after rubbing.

> OCR GCSE Physics A: Gateway Science (J249) — P3.1 Static and charge · Explain · 4 marks

> When certain insulating materials are rubbed together, electrons can be transferred from one material to the other, causing both objects to become electrically charged.

## Mark scheme (4 marks)

1. Electrons are transferred from the cloth to the ruler (during rubbing)
2. The ruler gains electrons and therefore has more electrons than protons, giving it a negative charge
3. The cloth loses electrons (to the ruler)
4. The cloth is left with a positive charge (equal and opposite to the charge on the ruler)

## Key terms

- [negatively charged](https://www.gradenine.co.uk/glossary/negatively-charged)
- [charge](https://www.gradenine.co.uk/glossary/charge)

## 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-student-rubs-a-plastic-ruler-87cb0536) · Published by Druglandscape Ltd.