ABSTRACT
Let a single turn coil be free to rotate at constant angular velocity symmetrically between the poles of a magnet system as shown in Fig. 14.1.
An e.m.f. is generated in the coil (from Faraday’s laws) which varies in magnitude and reverses its direction at regular intervals. The reason for this is shown in Fig. 14.2. In positions (a), (e) and (i) the conductors of the loop are effectively moving along the magnetic field, no flux is cut and hence no e.m.f. is induced. In position (c) maximum flux is cut and hence maximum e.m.f. is induced. In position (g), maximum flux is cut
and hence maximum e.m.f. is again induced. However, using Fleming’s right-hand rule, the induced e.m.f. is in the opposite direction to that in position (c) and is thus shown as −E . In positions (b), (d), (f) and (h) some flux is cut and hence some e.m.f. is induced. If all such
positions of the coil are considered, in one revolution of the coil, one cycle of alternating e.m.f. is produced as shown. This is the principle of operation of the a.c. generator (i.e. the alternator).
