What is the primary difference between the DC and AC motor? Is there any similarity in their rotors?
Alternating current motors have an electrical source which changes direction on a regular basis through the armature. This shift in polarity allows the armature to create a magnetic field that is of the same polarity of the magnet that the armature is near; these repulse, causing the armature to rotate. By the time it is in line with the other pole of the magnet, by which the armature is attracted and may possess enough strength to halt the rotation, the current has shifted direction, creating another magnetic field, but opposite in polarity to the first, which again is repulsed by the magnet opposite pole, creating a condition where North - North and South - South magnetic and electric fields are always aligning and repulsing, and so keeps the armature rotating.
Direct current motors have an electrical source which does not change direction; current always flows the same way. However, the armature of such motors possesses a slip ring commutator, which forces the current to flow in one direction through the armature, but then backwards through the armature by the time it has rotated in line with the magnet, again creating repelling electric and magnetic fields, causing the armature to rotate.