\documentclass[tikz, margin=15px]{standalone}
\usepackage{color,graphicx,circuitikz}
\usepackage[load-configurations=version-1]{siunitx}
\usetikzlibrary{arrows}
\begin{document}
 
\begin{circuitikz}[american, very thick]
\draw

	(0,1) -| (1,2)
	to [R, l=\huge{$R_C$}] (6,2) |- (7,1)
	(0,1) -| (1,0)
	to [C, l_=\huge{$X_C$}] (6,0) |- (7,1)

	(0,5) to [R, l=\huge{$R_C$}] (3.5,5) to [C, l=\huge{$C$}] (7,5)

	{(0,6) node {\Large{a)}} (0,2.5) node {\Large{b)}}}
;\end{circuitikz}
 
\end{document}