An inductor of inductive reactance $R$, a capacitor of capacitive reactance $2 R$ and a resistor of resistance $R$ are connected in series to an AC source. The power factor of the series $L-C-R$ circuit is

An inductor and a resistor are connected in series to an AC source of 10 V . If the potential difference across the inductor is 6 V , then the potential difference across the resistor is

In a series $L-C-R$ circuit, if the current leads the source voltage, then

A coil has a resistance of $30 \Omega$ and an inductive reactance of $20 \Omega$ at 50 Hz frequency. If an AC source of $200 \mathrm{~V}, 100 \mathrm{~Hz}$ is connected across the coil, the current in the coil is