Calculate the number of poles of synchronous motor if the synchronous speed is 1200 rpm. Given. supply frequency = 60 Hz.

Correct option is D

$$\text{The synchronous speed } N_s \text{ of a synchronous motor is given by:} \\\\N_s = \frac{120f}{P} \\\\\text{where } N_s \text{ is in rpm, } f \text{ is the frequency (Hz), and } P \text{ is the number of poles.} \\\\\text{Given } N_s = 1200\ \text{rpm and } f = 60\ \text{Hz:} \\\\1200 = \frac{120 \times 60}{P} \\\\P = \frac{120 \times 60}{1200} = 6 \\\\\text{Therefore, the correct answer is (d) 6.}$$​​