Question

An electromagnet
(A) Has its persistent magnetic field
(B) Acts as a magnet when an electric current passes through it
(C)Both (A) and (B)
(D) None of the above

Answer 1

Hint: An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. An electromagnet acts as a magnet when an electric current passes through it. In electromagnets, the magnetic field in the electromagnet is given by ampere’s law which shows the relationship between the magnetic field produced is equal to the sum of current flowing.

Complete answer:
Electromagnets are a wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole, denoting the center of the coil. The magnetic field vanishes when no current is flowing through the circuit. The wire turns around the magnetic core and is made of ferromagnetic or ferromagnetic material like iron, etc.
When an electric current is flowing through the wire it creates the magnetic fields around it due to the ampere's law. To concentrate the field in an electromagnet the wire is wound around it.the magnetic field of the electromagnet is given by Ampere’s law. It states that the integral value of the magnetic field around the closed-loop of the field is equal to the sum of the current flowing through the looped wire.
$\int {{\text{J}}{\text{.dA = }}\oint {{\text{H}}{\text{.dI}}} } $, where, $H$ is a magnetic field in closed-loop, $J$ is equal to the current produced
In the above options, the option(A) cannot be true as the magnetic field is produced only when the current is flowing through it. It never remains continuously flowing through the loop.
In other words, we can say that electromagnets act as the magnet when the current flows through it.

$\therefore$ Option (B) is the correct answer.

Additional information:
Electromagnets are made of the soft metal core.
(i) The material of a magnetic core is composed of small regions called magnetic domains; they act like tiny magnets. Before the current in the electromagnet is turned on, the domains in the iron core point in random directions, so their magnetic fields cancel out each other.
(ii) On passing through the wrapped wire around the iron, the magnetic field develops and penetrates through it and the domain aligns parallel to the magnetic field.
(iii)The effect of the core is to concentrate on the field.
(iv) The more current passed through the coil more the domains align and produce a stronger magnetic field. All the domain aligns in such a way that it increases the current only slight increase in the magnetic field is called saturation.
(v) When current is turned off the domain loses its alignment and returns to its random state and the magnetic field vanishes.

Note:
An electromagnet acts as a magnet when an electric current passes through it.
Used as the component of electrical devices such as solenoids, MRI machines, loudspeakers, etc