A device that changes one energy type into another
Microphone
Transfers sound energy into electricity
Loudspeaker
Transfers electricity into sound
Loudspeaker
Annularpermanent magnet
Cardboard cone diaphragm
Tube with wire coil wound around it (solenoid)
Coil fits snugly into circular cavity of magnet
How a loudspeaker works
1. Motor effect: Current flows in solenoid, magnetic field interacts with permanent magnet, solenoid and diaphragm pushed out or pulled in, creates compression wave that spreads out as longitudinal sound wave
2. Output frequency matches input AC signal
3. Loudness depends on magnitude of voltage signal
How a microphone works
1. Incoming sound wave causes membrane to move, solenoid moves to and fro over magnet, generates small electrical current in wire coil by electromagnetic induction (generator effect)
2. Output frequency matches incoming sound signal
3. Output signal is usually very weak and needs amplifying
