The armature and field windings have quite a large reactance at 50 or 60 Hz. A significant part of the input voltage is dropped across these reactances, and therefore Ell is smaller for a given input voltage during ac operation than it is during dc operation. Since Ell = Kcpw, the motor is slower for a given annature current and induced torque on alternating current than it wou ld be
on direct current.