ABSTRACT
Unlike direct currents that have steady values and always flow in the same direction, alternating currents (ACS) flow alternately one way and then the other. An understanding of alternating currents and voltages is important in a number of applications including AC power distribution, amplifiers and filters. The average value of an alternating current which swings symmetrically above and below zero will obviously be zero when measured over a long period of time. When two waveforms of same frequency are being compared it can be useful to compare them on the basis of the difference in angle that exists between their respective zero voltage crossing points. The current and voltage will both have sinusoidal shape and, since they rise and fall together, they are said to be in-phase with one another. Phasor diagrams provide us with a quick way of illustrating the relationships that exist between sinusoidal voltages and currents in AC circuits without having to draw lots of time-related waveforms.
