Correct Answer - Option 4 : 2 f ϕ V
In Alternator due to relative movement between conductor and magnetic field an EMF is induced in the stator conductor (Faraday’s Law of electromagnetic induction).
P = Number of poles
φ = Useful flux per pole in weber
f = Frequency of the induced emf equal to (NP/120) Hz
N = Rotational speed in rpm
Total flux cut to complete one revolution = Pφ
Time taken to complete one revolution = 60/N
According to faraday's law of electromagnetic induction
Average emf induced/conductor = Flux cut/time taken \( = \;\frac{{Pϕ }}{{\frac{{60}}{N}}} = \;\frac{{Pϕ N}}{{60}} = \;\frac{{Pϕ }}{{60}} \times \frac{{120f}}{P} = 2fϕ \)
∴ Average EMF induced per conductor is 2fϕ volts.