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

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

im sorry i dont know