CHAPTER 2 – AC Circuits

This chapter deals with the steady-state analysis of AC circuits. The simplest and widely occurring time-varying voltages and currents are sinusoidal. Nonsinusoidal waveshapes that drive circuits produce responses that vary substantially–to the point that the response has no resemblance to the source variation. It is only the sinusoid that could develop the phasor methodfor AC circuit analysis. If the voltage or current source is sinusoidal, all voltages and currents anywhere in the linear circuit will also be sinusoidal. Therefore, if it is desired to know a voltage somewhere in the circuit, all that remains to be solved for are the amplitude and phase angle of the unknown voltage. Phasor analysis, by introducing complex quantities, provides a method to analyze single-frequency circuits as easily as analyzing DC circuits. Since the impedance of inductors and capacitors depends on frequency, these elements are basic components in networks that are frequency sensitive and frequency selective. Band-pass filters can be used as tuning circuits where they allow one station or one channel out of many to be selected. The simplest band-pass filters are resonant circuits. Frequency selectivity of resonant circuits can be determined by the bandwidth. Transformers are also very efficient devices for changing the levels of AC currents, voltages, and impedances.