Question

The value of current at resonance in series $LCR$ circuit is affected by the value of

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

Answer 1

Answer: (A)

Let $E$ be the emf of the series LCR circuit, then current $(I)$ is given by
$I=\frac{E}{Z}$

where $Z$ is impedance.
$Z=\sqrt{R^2+{\left(\omega L-\frac{1}{\omega C}\right)}^2}$
At resonance $\omega L=\frac{1}{\omega C}$
$\therefore Z=R$
Hence, current $I=\frac{E}{R}$, depends on the value of $R$ only.