Question 11.SP.7: Find the phase angle for the following ac waves (Fig. 11-21)......
Find the phase angle for the following ac waves (Fig. 11-21) and draw their phasor diagrams.
To determine the phase angle, select a corresponding point on each wave. The maximum and zero crossing corresponding points are convenient. The angular difference of the two points is the phase angle. Then compare the two points to decide if one wave is in phase with, leading, or lagging the other wave.
In Fig. 11-21a, curves v and i reach their maximum values at the same instant, so they are in phase (the phasor diagram is as shown).
In Fig. 11-21b curve v reaches its zero value at a, 45° before curve i is zero at the corresponding point b, so v leads i by 45° (phasor diagram as shown).
In Fig. 11-21c, curve i reaches its maximum at b before curve v reaches its maximum at a so i leads v by 45° (phasor diagram as shown).
