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  MOVING COIL MICROPHONE 

                    When wire is moved within a magnetic field a current is generated in the wire. Using this induction principle, the dynamic microphone uses a wire coil, magnet, and a thin diaphragm to capture the audio signal.

The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates an electrical current in the coil, which is channeled from the microphone along wires. 

 MOVING COIL LOUD SPEAKER

                                The loudspeaker produces sound by converting electrical signals from an audio amplifier. Sound is created from the forward and backward motion of the loudspeaker cone. The cone is mounted and centered on a concave metal frame by a ring of flexible rubber. Glued to the center of the cone is a hollow cylinder. A length of thin, insulated wire is wound upon the bobbin to form the voice coil; both ends of the voice coil wire are connected to the voice coil terminals on the frame. The voice coil is positioned inside a narrow cylindrical groove or air gap in the center of a magnet. The coil is suspended in the air gap by a flexible fabric disc. An audio amplifier is connected to the voice coil terminals. The coil emits a magnetic field as audio signals from the amplifier travel through the voice coil wire. The voice coil field alternately pulls and pushes the coil, bobbin and cone assembly towards and against the magnetic field from the magnet, which causes the forward and backward cone motion.