# A security system uses a microphone to detect sounds in a building. The microphone produces an oscillating current that is sent to a monitoring device. Describe what is meant by an oscillating current and explain why the current produced by the microphone oscillates.

> Eduqas GCSE Physics — 8.4 Microphones, speakers, oscillating currents in detection · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. An oscillating current is one that repeatedly changes direction (alternates) / varies in size and direction over time
2. Sound waves cause the diaphragm of the microphone to vibrate
3. The vibrating diaphragm causes a coil (attached to it) to move back and forth inside a magnetic field
4. The coil cutting through the magnetic field induces a current / voltage that changes direction as the coil reverses, producing an oscillating current

## Key terms

- [oscillating current](https://www.gradenine.co.uk/glossary/oscillating-current)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-security-system-uses-a-microphone-71c41d91) · Published by Druglandscape Ltd.