Answer / 7anoter4

The a.c. electricity is produced in an a.c. generator which transform mechanical energy [from a turbine or diesel motor or else] into electrical energy.
In a synchronous generator the rotor produce a magnetic field -as permanent magnet or from d.c. current flowing through wired bobbins.
Let's take a single loop of the stator coil and expose it to a rotating magnetic field.
The EMF [electromotive force=induced voltage in the loop] =E=-dΦ/dt where:
Φ=magnetic flux through one stator [armature] loop
E=Electromotive Force [induced voltage]
Since the armature [stator] loop does not move then the magnetic flux shared with the loop is changing with the angle between loop surface and rotor pole surface. Φ=BxAxcos(α).where:
B =magnetic flux density produced from magnetic pole
A=magnetic pole area
rpm=no.of rotations per minute
Finally, E=BxAxsin(ωxt) where ω=2xπxpxRPM/60 p=no.of pole pairs t=time
That means the produced voltage depends on sinus of time.

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