# The average EMF per conductor in an alternator is:

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The average EMF per conductor in an alternator is:

1. 2π f ϕ V
2. 2.2 f ϕ V
3. ${2 \over \pi } f ϕ ~\;V$
4. 2 f ϕ V

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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.