The resonant frequency of a circuit is $f$. If the capacitance is made $4$ times the initial value,then the resonant frequency will become

$A$ series $LCR$ circuit is connected to an ac source of $220\,V, 50\,Hz$. The circuit contains a resistance $R=100\,\Omega$ and an inductor of inductive reactance $X_L=79.6\,\Omega$. The capacitance of the capacitor needed to maximize the average rate at which energy is supplied will be $..........\mu F$.

What will be the reading of the voltmeter in the given circuit (in $V$)?

The output voltage (taken across the resistance) of an $L-C-R$ series resonant circuit falls to half its peak value at a frequency of $200 \,Hz$ and again reaches the same value at $800 \,Hz$. The bandwidth of this circuit is ............. $\,Hz$.

In an $LCR$ resonant circuit,the phase difference between the current and the voltage is:

The current in resistance $R$ at resonance is