Alternating voltages and currents

The a.c. generator

 

Let a single turn coil be free to rotate at constant angular velocitysymmetricallybetween the poles of a magnet system as shown in FigureAn 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 Figure 14.2. In positions (a), (e) and (i) the conductors

and hence no e.m.f. is induced. In position (c) maximum flux is cut andhence 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 ac generator