Q.Explain one application of an electromagnet.

[!TLDR] One example: in an electric bell, current through a solenoid magnetises a soft-iron core, which attracts an armature to strike the gong and simultaneously breaks the circuit at a contact point, demagnetising the core and letting a spring reset it -- repeating rapidly to make …

Section 11.7 lists several applications of electromagnets -- electric bells, loudspeakers, circuit breakers, research-laboratory magnets, and cranes for lifting heavy iron loads -- all of which rely on the same switchable-magnetism property of a soft-iron core in a solenoid. Taking the electric bell as the worked example: pressing the bell's push-button completes a circuit that sends current through a solenoid wound around a soft-iron core; the resulting strong magnetic field attracts a nearby iron armature (attached to a small hammer), which swings to strike the bell's gong. As the armature moves, it also breaks contact at a point in the same circuit, cutting off the current; with no current, the soft-iron core's low retentivity means it demagnetises almost immediately, releasing the armature, which springs back under a restoring spring -- remaking the contact and restarting …

Pick one application listed in section 11.7 and explain the mechanism by which its switchable (soft-ir …

Describing an application that actually needs a PERMANENT magnet (a durable, always-on field) rather than one that specifical …