Teach Yourself Electricity and Electronics, Sixth Edition, 6th Edition

12

CHAPTER

Phase

IN AN AC WAVE, EVERY FULL CYCLE REPLICATES EVERY OTHER FULL CYCLE; THE WAVE REPEATS INDEFInitely. In this chapter, you’ll learn about the simplest possible shape (or waveform) for an AC disturbance. We call it a sine wave or sinusoid.

Instantaneous Values

When we graph its instantaneous amplitude as a function of time, an AC sine wave has the characteristic shape shown in Fig. 12-1. This illustration shows how the graph of the function y = sin x looks on an (x,y) coordinate plane. (The abbreviation sin stands for sine in trigonometry.) Imagine that the peak voltages equal +1.0 V and −1.0 V. Further imagine that the period equals exactly one second (1.0 s) so the wave has a frequency of 1.0 Hz. Let’s say that the wave begins at ...