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Alternating Current and Voltage - Engineering

Q1:

To produce an 800 Hz sine wave, a four-pole generator must be operated at

A 200 rps

B 400 rps

C 800 rps

D 1,600 rps

ANS:B - 400 rps

N = 120f/P.

where N=speed in rpm.
f = frequency.
P = Numbers of poles.
then calculate;
N=?, f = 800Hz, P = 4,
N=120 * 800/4.
= 24,000rpm
then 24,000 convert into rps because options are given in rps that's why we convert into rps.
i.e 24,000/60 = 400rps.