Magnet , around for ferrite and SmCo, about for NIB and lower for flexible ceramics, but the exact numbers depend on the grade of material. An electromagnet, in its simplest form, is a wire that has been coiled into one or more loops, known as a solenoid. When electric current flows through the wire, a magnetic field is generated. It is concentrated near (and especially inside) the coil, and its field lines are very similar to those of a magnet. The orientation of this effective magnet is determined by the right hand rule. The magnetic moment and the magnetic field of
Voice coil to refer to the coil of wire that moves the read–write heads in a moving-head disk drive. In this application, a very lightweight coil of wires is mounted within a strong magnetic field produced by permanent rare-earth magnets. The voice coil is the motor part of the servo system that positions the heads: an electric control signal drives the voice coil and the resulting force quickly and accurately positions the heads. Voice coil A voice coil (consisting of a former, collar, and winding) is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive