Chapter 2- Sinusoidal steady state analysis
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Alternating currents are more widely used in the field of power and electronics than direct current. By the term alternating, it is meant that the current is not unidirectional but assumes alternately positive and negative values. Unlike the flow of direct current, there is no electron drift in a conductor carrying alternating current, but they merely oscillate about their average positions inside the conductor. If we plot an alternating current changing with time as a graph, with time in the X-axis and current in the Y-axis, we get the waveform of the alternating current. Sinusoidal wave alternating current is what we use in A.C. power circuits. Other waveforms like a triangular wave, square wave are used only in electronic circuits.
Fig. 2.1(c) shows a random waveform. Such waveforms are not classified as alternating currents. Only those waves which are periodic i.e., repeat themselves in a definite pattern are amenable for study. Even among these periodic waves, the sinusoidal (sine and cosine) waveform is of fundamental importance. Fourier, a mathematician, showed that all periodic waveforms (sinusoidal or not) can be split up into a series of sinusoidal waves. So, a study of the behaviour (response) of circuit elements to steady sinusoidal voltages (or currents) will be made in this chapter. The response to any other a.c. wave of voltage (or current) will be the sum of the responses of the Fourier components of the waveform.