Question

A coil, a capacitor and an $AC$ source of rms voltage $24V$ are connected in series. By varying the frequency of the source, a maximum rms current of $6A$ is observed. If coil is connected to a dc battery of emf $12$ volt and internal resistance $4\Omega$, then current through it in steady state is :

• A. $2.4A$
• B. $1.8A$
• C. $1.5A$
• D. $1.2A$

Answer 1

The correct option is C $1.5A$

$I_{rms}=\frac{V}{R}$ (at resonance)
$6=\frac{24}{R}$
$\therefore R=4\Omega$
$I_{dc}=\frac{V}{R+r}=\frac{12}{4+4}=1.5A$