Complex Numbers and Phasors

Summary

When dealing with complex numbers, it is often expedient to represent them graphically. One can easily do that in a complex plane using a Cartesian coordinate system, where the x axis is the real axis and the y axis is the imaginary axis. In electromagnetics problems, it is often practical to represent a complex number z as a directed line segment from the origin to the point P in the complex plane. In electromagnetic compatibility the authors often deals with complex voltages and currents. These complex expressions represent sinusoids in the time domain, and therefore they are phasors. They also encounter complex impedance, but the impedance does not represent a time‐domain sinusoid, so it is not a phasor, but just a complex expression. Of major interest in EMC are the sinusoidal electromagnetic fields and current and charge densities. That is, the time‐domain vectors and scalar expressions are sinusoidal functions of time and space.