How does a loudspeaker work?
A loudspeaker turns an electrical signal into sound using the motor effect.
GCSE Physics
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
In more detail
A varying current from the amplifier flows through a coil that sits in the field of a permanent magnet. The motor effect produces a force on the coil, and because the current is constantly varying, the coil (and the paper cone attached to it) moves in and out. This pushes and pulls the air, creating pressure variations — sound waves — that match the original signal.
Key points for the exam
- It relies on the motor effect (force on a current-carrying conductor in a field).
- The cone’s vibration frequency sets the pitch; its amplitude sets the loudness.
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