“Hybrid” ac/dc combinations are not often generated deliberately. But such wave-forms are sometimes seen at certain points in electronic circuitry.The ac generator Alternating current is easily generated by means of a rotating magnet in a coil of wire(Fig. 9-14A), or by a rotating coil of wire inside a powerful magnet (Fig. 9-14B). In ei-ther case, the ac appears between the ends of the length of wire.The ac voltage that a generator can develop depends on the strength of the mag-net, the number of turns in the wire coil, and the speed at which the magnet or coil ro-tates. The ac frequency depends only on the speed of rotation. Normally, for utility ac,this speed is 3,600 revolutions per minute (rpm), or 60 complete revolutions per sec-ond (rps), so that the frequency is 60 Hz.176 Alternating current basics9-12Connection of a dcsource in series with anac source.9-13Waveform resulting from 117 Vac in series with + 200 Vdc.