# A microphone converts sound waves into electrical current variations. Explain how a microphone works, and describe how a loudspeaker then uses those current variations to reproduce sound.

> Edexcel A-Level Physics (9PH0) — 13.1 Simple harmonic motion and damping · Explain · 5 marks

> A singer performs into a microphone connected by a wire to a loudspeaker. The loudspeaker reproduces the sound on the other side of a large stage.

## Mark scheme (5 marks)

1. Pressure variations in the sound waves cause the coil (in the microphone) to move
2. The moving coil passes through the magnetic field of the fixed magnet, inducing a current / potential difference in the coil (generator effect)
3. The induced current varies in proportion to (mirrors) the pressure variations of the original sound wave
4. In the loudspeaker, the varying current flows through a coil situated in the field of a fixed magnet, causing a force on the coil making it move
5. The moving coil causes the cone / diaphragm to vibrate, producing pressure variations in the air which are heard as sound

## Key terms

- [microphone](https://www.gradenine.co.uk/glossary/microphone)
- [loudspeaker](https://www.gradenine.co.uk/glossary/loudspeaker)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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-microphone-converts-sound-waves-into-41ff7277) · Published by Druglandscape Ltd.