It should be apparent by
now that if the current flowing into the slotted stator is alternating, the direction of
the flux will also alternate, so that in effect the two poles will reverse polarity every
time the current reverses direction, that is, every half-cycle of the sinusoidal current.
Further—since the magnetic flux is approximately proportional to the current in
the coil—as the amplitude of the current oscillates in a sinusoidal fashion, so will
the flux density in the structure.