Q. In a series resonant L – C – R circuit, the voltage across R is 100 V and $R\ = \ 1\ k\ \Omega$ with $C = 2\mu F$. The resonant frequency $\omega$ is $200\ $rad$s^{- 1}.$ At resonance the voltage across L is

A) $2.5 \times 10^{- 2\ }V$
B) 40 V
C) 250 V
D) $4 \times 10^{- 3\ }V$
Explanation

(c) At resonance, $\omega L = \frac{1}{\omega C}$
Current flowing through the circuit,
$I = \frac{V_{R}}{R}$
$= \frac{100}{1000} = 0.1\ A$
So, voltage across L is given by
$V_{L} = IX_{L} = I\omega L$
But $\omega L = \frac{1}{\omega C}$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ V_{L} = \frac{1}{\omega C}$
$= \frac{0.1}{200 \times 2 \times 10^{- 6}} = 250\ $V

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.