In a series $R-L-C$ circuit,the frequency of the source is half of the resonance frequency. The nature of the circuit will be

The $Q$-factor of a resonant circuit is equal to

An $AC$ circuit consists of an inductor of inductance $0.5 \, H$ and a capacitor of capacitance $8 \, \mu F$ in series. The current in the circuit is maximum when the angular frequency of the $AC$ source is

An a.c. e.m.f. of peak value $230 \ V$ and frequency $50 \ Hz$ is connected to a circuit with $R=11.5 \ \Omega, L=2.5 \ H$ and a capacitor all in series. The value of capacitance is '$C$' for the current in the circuit to be maximum. The value of '$C$' and maximum current are respectively $(\pi^2=10)$

$A$ 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 $..........\mu F$.

In a series $L-C-R$ circuit,the capacitance is changed from $C$ to $2C$. To obtain the same resonance frequency,the inductance should be changed from $L$ to: