Operations on sinusoidal variables based on the trigonometric identities are in general lengthy and tedious. The phasor method can convert such sinusoidal variables to vectors in complex plane and thereby simplify the operations. A sinusoidal time function can be considered as the real (or imaginary) part of a rotating vector in the complex plane. If two sinusoidal functions have the same frequency , i.e., they are rotating at the same rate, their relative positions with respect to each other are fixed independent of . Therefore the vectors can be considered as static instead of rotating if observed from a reference frame rotating at the same frequency as the vectors. An operation of two sinusoids can be carried out on their phasors, and the resulting phasor can then be converted back to a sinusoidal time function by taking the real part of the phasor now assumed to be rotating.

As useful and as easy to understand as DC is, it is not the only “kind” of electricity in use. Certain sources of electricity (most notably, rotary electro-mechanical generators) naturally produce voltages alternating in polarity, reversing positive and negative over time. Either as a voltage switching polarity or as a current switching direction back and forth, this “kind” of electricity is known as Alternating Current (AC): 

SINUSOIDAL STEADY STATE CIRCUIT ANALYSIS (3.5 & 3.6 Power AC Circuits) - download at 4shared. 3. SINUSOIDAL STEADY STATE CIRCUIT ANALYSIS (3.5 & 3.6 Power AC Circuits) is hosted at free file sharing service 4shared.

Fundamentals of Circuit analysis with illustrations and graphs.

Powerpoint presentation of the basic Ac circuit analysis techniques known.

An ac circuit may contain a number of series and/or parallel branches. As will be studied in the following paragraphs, however, it is possible to divide any complex ac circuit into subcircuits that include simple circuit combinations. Therefore, five ac circuit combinations are identified and studied here: equivalent impedance circuit, voltage divider circuit, current divider circuit, series/parallel (combination) circuit, and circuit with dual ac supply.
The equivalent impedance of any number of impedances in series or in parallel (Fig. 3-2) is the sum of the individual impedances or the sum of the admittances that is equal to 1/Z, respectively.

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