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

A capacitor of capacitance ' C ' is connected across a.c. source of voltage V as $\mathrm{V}=\mathrm{V}_0 \sin \omega \mathrm{t}$. The displacement current between the plates of the capacitor would be

A resistor of $400 \Omega$, an inductance of 0.4 H are in series with an a.c. source of e.m.f. $\mathrm{E}=200 \sqrt{2} \sin (1000 \mathrm{t})$. The power factor of the circuit is