Question

ln an AC circuit, the current lags behind the voltage by $\pi$/3. The components of the circuit are

• A. R and L
• B. L and C
• C. R and C
• D. only R

Answer 1

Answer: (A)

R and L

Answer 2

Since, current lags behind the voltage in phase by a constant angle, then circuit must contain R and L.
We find that in R-L circuit, voltage leads the current by a phase angle $\phi$, where

$\tan \phi = \frac{ AK}{ OA} = \frac{ OL}{ OA}$
$= \frac{ V_L}{ V_R} = \frac{ I_0 \, X_L}{ I_0 R}$
$\therefore tan \, \phi = \frac{ X_L}{ R}$