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15<br />

Series and Parallel<br />

ac Circuits<br />

15.1 INTRODUCTION<br />

In this chapter, phasor algebra will be used to develop a quick, direct<br />

method for solving both the series and the parallel ac circuits. The close<br />

relationship that exists between this method for solving for unknown<br />

quantities and the approach used for dc circuits will become apparent<br />

after a few simple examples are considered. Once this association is<br />

established, many of the rules (current divider rule, voltage divider rule,<br />

and so on) for dc circuits can be readily applied to ac circuits.<br />

SERIES ac CIRCUITS<br />

15.2 IMPEDANCE AND THE PHASOR DIAGRAM<br />

Resistive Elements<br />

In Chapter 14, we found, for the purely resistive circuit of Fig. 15.1,<br />

that v and i were in phase, and the magnitude<br />

Im � � Vm<br />

� or Vm � ImR R<br />

i = I m sin qt<br />

+<br />

R v = Vm sin qt<br />

–<br />

FIG. 15.1<br />

Resistive ac circuit.<br />

a c

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