Question

Voltage and current in an ac circuit are given by

$V = 5\sin\left( 100\pi t - \frac{\pi}{6} \right)$ and $i = 4\sin\left( 100\pi t + \frac{\pi}{6} \right)$

• A. Voltage leads the current by 30°
• B. Current leads the voltage by 30°
• C. Current leads the voltage by 60°
• D. Voltage leads the current by 60°

Answer 1

Answer: (C)

Current leads the voltage by 60°

Answer 2

Phase difference relative to current $\Delta\varphi = - \frac{\pi}{6} - \frac{\pi}{6} = - \frac{\pi}{3}$

In degree $\Delta\varphi = - 60^{o}$ i.e. voltage lag behind the current by 60^o or current leads the voltage by 60^o.