Phasors replace the passage of time with the geometry of relationship

A phasor diagram is a graphical representation of sinusoidal quantities, such as voltage and current, that have the same frequency but differ in magnitude and phase. Each quantity is represented by a vector, or phasor, whose length indicates amplitude and whose angle indicates phase relative to a reference. Because the common oscillation with time is omitted, the diagram turns relationships between changing waveforms into a simpler geometric problem. Phasors make it easy to see phase differences, add sinusoidal signals, and analyze the effects of resistance, capacitance, and inductance. They are used in AC circuit analysis, signal processing, and control systems.