How the moving coil actuator work?

Answer 1

A loudspeaker produces sound by converting electrical signals from an audio amplifier into mechanical motion. Sound is created from the forward and backward motion of the loudspeaker cone, which is a concave plastic or paper disc. The cone is mounted and centred on a concave metal frame by a ring of flexible rubber. Glued to the centre of the cone is a hollow cylinder of thin, lightweight aluminium. 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 centre 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.

Answer 2

Instrument used to detect and measure electrical current. A coil of wire pivoted between the poles of a permanent magnet is turned by the motor effect of an electric current (by which a force acts on a wire carrying a current in a magnetic field). The extent to which the coil turns can then be related to the magnitude of the current. The sensitivity of the instrument depends directly upon the strength of the permanent magnet used, the number of turns making up the moving coil, and the coil's area. It depends inversely upon the strength of the controlling springs used to restrain the rotation of the coil. By the addition of a suitable large resistor, a moving-coil meter can be adapted to read potential difference in volts. A simple moving-coil meter. Direct electric current (DC) flowing through the wire coil combined with the presence of a magnetic field causes the coil to rotate; this in turn moves a pointer across a calibrated scale so that the degree of rotation can be related to the magnitude of the current.