If the AC voltage and current are given by the following expressions?v = 200sin (314t — 60°)i = 50sin (720t), then what is the phase relation between them?

• A. Voltage and current are in phase
• B. Voltage lags current by 60°
• C. Voltage leads current by 60°
• D. Can’t be determined

Answer: (D)

When two alternating quantities of the same frequency have different zero points, they are said to have a phase difference. The angle between zero points is the angle of phase difference φ.
In the above-given question, the frequency of voltage and current is different so we can’t calculate the phase difference between them