Q. A six pole generator with fixed field excitation developes an emf of 100 V, when operating at 1500 rpm. At what speed must it rotate to develop 120 V?
A) 1200 rpm
B) 1800 rpm
C) 1500 rpm
D) 400 rpm
Explanation
(b) The emf induced is directly proportional to rate at which flux is intercepted which varies directly as the speed of rotation of the generator.
New, speed=$\frac{120}{100} \times 1500\ rpm = 1800\ rpm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.