# A doctor uses an ultrasound device that contains a loudspeaker to direct sound waves into a patient's body. Explain how the loudspeaker in the device converts an oscillating electrical current into sound waves.

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

> Ultrasound devices used in medicine contain loudspeakers that receive oscillating electrical signals and produce sound waves at frequencies above the range of human hearing.

## Mark scheme (4 marks)

1. The oscillating current passes through the coil (attached to the cone/diaphragm)
2. The coil experiences a force due to the interaction between the current and the magnetic field (of the permanent magnet)
3. Because the current oscillates, the force on the coil (and cone) reverses repeatedly / the coil moves back and forth
4. The vibrating cone causes compressions and rarefactions in the surrounding medium, producing sound waves

## Key terms

- [sound waves](https://www.gradenine.co.uk/glossary/sound-waves)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-doctor-uses-an-ultrasound-device-f249b46e) · Published by Druglandscape Ltd.