Consider a DC voltage source connected to a series R-C circuit. When the steady-state reaches, the ratio of the energy stored in the capacitor to the total energy supplied by the voltage source, is equal to

A series LCR circuit consisting of $$R = 10\Omega $$, $$\left| {{X_L}} \right|\,\,\, = 20\Omega $$ and $$\left| {{X_C}} \right|\,\,\, = 20\Omega $$, is connected across an a.c. supply of $$200V$$ rms. The rms voltage across the capacitor is

In the series circuit shown in figure, for series resonance, the value of the coupling coefficient K will be