Which is an important step in how an electric motor uses magnetic force to produce motion?
a) as the north pole of the electromagnet nears the north pole of the permanent magnet, the current reverses and the poles of the magnets then attract.
b) as the north pole of the electromagnet nears the south pole of the permanent magnet, the current reverses and the poles of the magnets then repel.
c) as the north pole of the electromagnet nears the north pole of the permanent magnet, the current reverses and the poles of the magnets then repel.
d) as the north pole of the electromagnet nears the south pole of the permanent magnet, the current reverses and the poles of the magnets then attract.

B) As the north pole of the electromagnet nears the south pole of the permanent magnet, the current reverses and the poles of the magnets then repel.

Explanation:

As we know that electric motor is based on the concept of torque due to magnetic field on current carrying coil.

Here as the current is passing through the coil the torque on the coil is given as

so here the magnetic field due to coil will continuously repelling the current carrying coil as it will move between the magnetic field so direction of current in the coil will change continuously so that it will always repel by the magnetic field and continuously rotated between the magnets

snell's law

refractve index = sin incidence / sin refraction