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
Trembler coil springy iron arm, which holds them closed. The arm is mounted near the iron core. When battery power is applied, the coil acts as an electromagnet; the magnetic field from the core pulls the springy iron arm, opening the switch contacts, interrupting the primary current. The magnetic field of the core is switched off, allowing the arm to spring back, closing the contacts again. Then the primary current is turned on again, and the magnetic field opens the contacts again. This cycle repeats many times per second, while power is applied to the coil. A similar mechanism is used in