A series LCR circuit is connected to an ac source of 220   V ,   50   Hz . The circuit…

The average rate at which energy supplied i.e. power delivered is maximum in case of the resonance, therefore

$X_C=X_L$

$\Rightarrow \frac{1}{\omega C}=79.6 \mathrm{\Omega }$

$$\begin{gathered} \Rightarrow C=\frac{1}{\omega \times 79.6} \\ =\frac{1}{2\pi f\times 79.6} \\ =\frac{1}{100\pi \times 79.6} \\ =40 \mathrm{\mu F} \end{gathered}$$

Hence, $C=40 \mathrm{\mu F}$.