What type of diagram shows the phase relationships between two or more alternating quantities?

The phasor diagram is the appropriate choice for illustrating the phase relationships between alternating quantities, such as voltage and current in electrical engineering. It represents sinusoidal functions as rotating vectors, or phasors. In this diagram, the length of each vector corresponds to the magnitude of the quantity, and the angle relative to a reference line indicates the phase of that quantity.

This graphical representation helps engineers and technicians understand how different alternating waveforms relate to each other in terms of their amplitude and phase differences. Phasor diagrams are particularly useful for analyzing circuits with sinusoidal steady-state conditions, as they simplify calculations involving complex numbers and angular relationships.

Other types of diagrams, such as waveform diagrams, focus on depicting the actual shape of alternating signals over time but do not clearly convey the phase relationship between multiple signals. Block diagrams represent systems and their components but do not detail timing or phase. Flowcharts provide a visual representation of processes and decision-making steps, which are unrelated to analyzing waveforms or phase angles.