Microphones (HT only) — AQA GCSE Physics
Test yourself on Microphones (HT only) with AQA GCSE practice questions.
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Microphones (HT only) explained
Build your explanation of a moving-coil microphone around the parts visible in a cross-section diagram.
Read the full explanation
The diaphragm is the thin sheet facing the sound, the coil is wound on a former fixed behind it, and the permanent magnet is fixed to the body. Explain the sequence: sound waves cause the diaphragm to vibrate, making the attached coil vibrate with it. As the moving coil cuts the magnetic field lines of the fixed magnet, a potential difference is induced across the coil. This induced potential difference drives a varying current around the circuit. A microphone uses the generator effect, whereas a loudspeaker uses the motor effect to transfer energy in the opposite direction.
Your focus
- Label the diaphragm, coil and magnet on a cross-section of a moving-coil microphone.
- Sequence an explanation running from the arriving sound wave to the induced current in the circuit.
- Compare a microphone with a loudspeaker in terms of which effect each uses and the direction of energy transfer.
Microphones (HT only) exam tips
Marking Points
- identifying that sound waves cause the diaphragm to vibrate
- stating that the coil is attached to the diaphragm and vibrates with it
- explaining that the moving coil cuts the magnetic field lines of the fixed permanent magnet
- stating that this induces a potential difference across the ends of the coil
- explaining that the induced potential difference drives a varying alternating current in the closed circuit
- comparing with a loudspeaker by stating the microphone uses the generator effect while the loudspeaker uses the motor effect
Examiner Tips
- 💡Annotate the diagram first, then write one sentence for each labelled part to build a logical sequence.
- 💡Ensure your explanation links cause and effect, from the arriving sound wave to the induced current.
Common Mistakes
- having the magnet move and the coil stay still, which contradicts standard microphone diagrams
- describing the current as being produced by the magnet rather than induced in the coil
- writing a sequence of steps with no cause linking them, such as jumping from sound arriving to current flowing without mentioning the coil cutting field lines
- claiming that a microphone and a loudspeaker are built from fundamentally different components