GCSE Physics (AQA)

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Microphones

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Magnetism and electromagnetism Induced potential, transformers and the National Grid

Microphones

4:33 Applying the Generator Effect
Spec 4.7.3.3
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  • Microphones use the generator effect to convert sound wave pressure changes into current variations.
  • To effectively use a microphone, it should be positioned so sound waves travel directly towards it.
  • Sound waves are created by the back-and-forth vibrations of air particles.
  • The microphone detects these vibrations and converts them into electrical current.
  • The microphone contains a coil attached to a pressure-sensitive diaphragm that vibrates in response to sound waves.
  • The diaphragm is a thin film that vibrates due to pressure changes and is connected to a coil of conducting wire.
  • The coil is placed around the poles of a magnet, inducing a potential difference in the coil as it vibrates.
  • The magnet has a north pole on the outside and a south pole in the center, creating a magnetic field directed towards the center.
  • As the coil moves back and forth due to sound waves, it cuts across the magnetic field lines, inducing a potential difference.
  • The induced potential difference and the resulting current have the same frequency as the incoming sound waves.
  • The direction of the induced potential difference reverses with the direction of the coil's motion, creating an alternating potential difference and current.
  • This alternating current carries the properties of the original sound waves and can be used in various applications.
  • Microphones can send electrical signals to circuits, which can be used as inputs for loudspeakers or analyzed with oscilloscopes to display sound properties like frequency and amplitude.
  • Loudspeakers convert electrical signals back into sound waves using the motor effect, often used in concerts and events.
  • Oscilloscopes analyze the electrical signal from microphones to display sound wave properties.
  • Microphones are also used for making audio recordings and as sound detectors.

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