Q 12-07-013NEETNEET 2020Top questionMedium
A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is $\dfrac{\pi}{3}$. If instead C is removed from the circuit, the phase difference is again $\dfrac{\pi}{3}$ between current and voltage. The power factor of the circuit is :
Answer: (C) $1.0$
L removed: $\tan\dfrac{\pi}{3} = \dfrac{X_C}{R}$. C removed: $\tan\dfrac{\pi}{3} = \dfrac{X_L}{R}$.
So $X_L = X_C$: with all three present the circuit is at resonance, $Z = R$ and $\phi = 0$.
$$\cos\phi = 1$$
Solution by Sreeraj P, M.Sc Physics