The correct answer is A. Magnetism that remains in
the core of an electromagnet after the current through the coil is turned off.Residual magnetism is the magnetism that remains in a ferromagnetic material after the external magnetic field that caused it has been removed. It is caused by the alignment of the magnetic domains in the material. When a ferromagnetic material is placed in a magnetic field, the domains align with the field.
When the field is removed, the domains tend to remain aligned, resulting in residual magnetism.The amount of residual magnetism depends on the material, the strength of the applied field, and the time the material is exposed to the field. Residual magnetism can be reduced by heating the material or by applying a reverse magnetic field.
Residual magnetism is used in a variety of applications, including electromagnets, loudspeakers, and magnetic recording.
Option B is incorrect because it describes the force of attraction between the poles of a permanent and temporary magnetic field.
Option C is incorrect because it describes the amount of magnetic flux that is not confined to the core material of an electromagnet.
Option D is incorrect because it describes the circular magnetic field that surrounds a conductor carrying a current.
Option E is incorrect because it is not a description of residual magnetism.