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Microphones and loudspeakers are everyday devices that use the principles of electromagnetism. Loudspeakers use the motor effect to convert electrical signals into sound, while microphones use the generator effect to convert sound into electrical signals. This is Higher tier content from AQA GCSE Physics specification 4.7.2 and 4.7.3.
A loudspeaker converts an electrical signal (alternating current) into sound waves.
| Component | Role |
|---|---|
| Permanent magnet | Provides a strong, constant magnetic field |
| Coil of wire (voice coil) | Carries the alternating current signal; attached to the cone |
| Paper or plastic cone | Vibrates to produce sound waves |
| Suspension (spider and surround) | Allows the cone to move back and forth freely |
graph LR
subgraph "Loudspeaker Cross-Section"
AC["AC Signal Input"] --> VC["Voice Coil (wrapped around former)"]
PM["Permanent Magnet (cylindrical)"] -.->|"Provides magnetic field"| VC
VC -->|"Motor effect: force on coil"| CONE["Paper Cone"]
CONE -->|"Vibrates"| SOUND["Sound Waves"]
end
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