Explain why the e.m.f. generated in a conductor of an

alternating-current generator is seldom sinusoidal.

A rectangular coil of 55 turns, carried by a spindle

placed at right angles to a magnetic field of uniform

density, is rotated at a constant speed. The mean area

per turn is 300 cm2. Calculate: (a) the speed in order

that the frequency of the generated e.m.f. may be

60 Hz; (b) the density of the magnetic field if the

r.m.s. value of the generated e.m.f. is 10 V.