What Is the Frequency in Hertz (Hz) of the Current

Short Answer

What is the frequency in hertz (Hz) of the current furnished by an alternator having 8 poles and running at a speed of 900 revolutions per minute? $$\begin{aligned}f = \frac { P N } { 60 } \quad \text { where } & f = \text { frequency in hertz } \\P & = \text { number of pairs of poles } \\N & = \text { revolution per minute }\end{aligned}$$