I am currently working with machines and when I try to understand their principles in-depth, specifically in machines, I got to know that EMF is induced because of any of the two reasons:
1) Time-varying magnetic field.
2) Spacial changes in the magnetic field.
It is said in sources I referred that in transformers the induced EMF is due to the time-varying magnetic field and in generator or motor, it is due to spacial variation in the magnetic field.
I did not get why in generators or motor the field is spatially varying. The magnetic field there also varies with respect to time because of sinusoidal current flowing through them?