Provide information about electromagnets.

(N/A) An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. It only exhibits magnetic properties while an electric current flows through the coil wound around a ferromagnetic core.
The core of an electromagnet is typically made of ferromagnetic materials.
These materials must have high magnetic permeability and low retentivity. Therefore,soft iron is an ideal material for electromagnets.
When a soft iron rod is placed inside a solenoid and an electric current is passed through it,the magnetic field of the solenoid increases by a factor of thousands.
When the current in the solenoid is switched off,the magnetism effectively disappears because the soft iron core has low retentivity.
In applications like transformer cores and telephone diaphragms,the material undergoes an $AC$ cycle of magnetization repeatedly. For such applications,the hysteresis curve of the material must be narrow to minimize energy dissipation and heating.
Additionally,the material must have high electrical resistivity to reduce energy losses due to eddy currents.