Electrodynamic moving-coil microphone
Microphones

A moving coil made up of N turns of length L (total length $\mathcal{l}$ = NL ) placed in a field of constant radial magnetic induction B is subjected to a force F (normal to B ) and moves at speed v, intersecting the induction lines (figure 10 ). It is therefore the seat of an induced electromotive force e.

The coil is attached to a diaphragm with surface area S. The assembly of coil and diaphragm is called the moving assembly.

The system...