Question

In an electric motor, periodically changing the electromagnet can cause the axle to spin because

Answer 1

We want to know why does the axle spin in the electric motor. When we periodically change the electromagnet via alternate current, the magnetic field reverses directions which creates a force on the axle and so the axle starts spinning. So the correct answer is d. the magnetic field reverses direction. 

Answer 2

The answers are,

B
B
D
D


Hope I helped!