Study Curve

I am assuming you are interested in an AC or alternating current motor. A direct current motor runs by running current through a split ring commutator (which allows the current to switch directions every time the loop passes 0 degrees or 180 degrees) as to cause torque on the loop and creating it to turn in the same direction. However, in an AC motor the current automatically reverses direction ever one-half cycle eliminating the need for a split ring commutator.