The term “phase” refers to the time relationships between sine waves in a circuit. The pointer system serves as a representation for describing the voltages in RC, RL, or RLC circuits, highlighting the time relationships between peak voltages and currents. In a capacitor, there’s a 90° phase lag, indicated by the voltage pointer being at right angles to the current pointer. Conversely, in an inductor, the voltage leads the current by 90°. The phase shift between pointers is expressed in degrees.
The phase relationship in an RL circuit can be calculated directly from the geometry of voltage and current pointers. Initially, the current pointer was positioned horizontally, simplifying the determination of the driving or input voltage. However, the inverse problem is often specified, necessitating the determination of the amplitude and phase angle of the resulting current. The phase angle is independent of the horizontal orientation of pointers and can be determined using any orientation, provided proper scaling.
The discussion assumes the steady-state condition for sinusoidal voltages and currents, with a transitional or transient period when a sine-wave voltage source is initially connected to a circuit. During this transient period, voltages and currents adjust to their steady-state condition, and the rotating pointers apply only to this condition.
Impedance, a sinusoidal concept applicable to linear components, is sometimes inaccurately applied to nonsinusoidal situations. Despite its convenient use, impedance is fundamentally a geometric concept, not dependent on the presence of voltages and currents for calculation.