An inductor of $0.5 \ mH$,a capacitor of $20 \ \mu F$ and a resistance of $20 \ \Omega$ are connected in series with a $220 \ V$ a.c. source. If the current is in phase with the e.m.f.,the maximum current in the circuit is $\sqrt{x} \ A$. The value of '$x$' is

$A$ series $LCR$ circuit with $R=20\; \Omega, L=1.5\; H$ and $C=35\; \mu F$ is connected to a variable-frequency $200\; V$ $ac$ supply. When the frequency of the supply equals the natural frequency of the circuit,what is the average power (in $W$) transferred to the circuit in one complete cycle?

In a series $LR$ circuit with $X_L = R$, the power factor is $P_1$. If a capacitor of capacitance $C$ with $X_C = X_L$ is added to the circuit, the power factor becomes $P_2$. The ratio of $P_1$ to $P_2$ will be:

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

In an $LCR$ circuit,the inductance is changed from $L$ to $9 L$. For the same resonant frequency,the capacitance should be changed from $C$ to:

In an $L-C-R$ circuit,the power factor at resonance is