Moving coil microphone

Moving coil microphone is also called dynamic microphone. Here we make use of the principle of electromagnetic induction. Whe sound pressure variations move a coil placed in a magnetic field, there is a change in magnetic flux passiong through the coil. Then an e.m.f is introduced in the coil. This forms the output of the microphone. A moving coil microphone is very much similar to a moving coil loudspeaker. Hence in office intercom systems, the same unit is used both as microphone and loudspeaker. The main components of a moving coil microphones are magnet, diaphragm and coil. The magnet is a permanent magnet of POT type with a central pole piece and the peripheral pole piece. Diaphragm is a thin circular sheet of nonmagnetic material and is of light weight. Coil is wound on a cardboard cylinder which is attached to diaphragm. The coil is single layered thin enamelled wire. A metal grill acting as a protective shield is used to save the delicate diaphragm and coil assembly from being mishandeled.