A.C. generators or alternators (as they are usually called) operate on the same fundamental principles of electromagnetic induction as D.C. generators. the speed at which the coil or magnetic field rotates. The induced emf in a coil in AC generator is given as
E = NABωsinθ
ω = dθ/dt
Now, when the angle between the normal of plane and magnetic field is zero degrees, the induced emf is zero i.e.
E = NABωsin0=0
