Q. An $LCR$ series circuit is at resonance. Then
A) The phase difference between current and voltage is $90{^\circ}$
B) The phase difference between current and voltage is $45{^\circ}$
C) Its impedance is purely resistive
D) Its impedance is zero
Explanation
(c) In series LCR, the impedance of the circuit is given by
$Z = \sqrt{R^{2} + \left( X_{L} - X_{C} \right)^{2}}$
At resonance, $X_{L} = X_{C}$
$\therefore Z = R$
At resonance, the phase difference between the current and voltage is $0{^\circ}$. Current is maximum at resonance
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.