% Author: Prof. Dr. Matthias Jung, DL9MJ
% Year: 2025
\begin{circuitikz}
    \draw (0,0)
        to [short] ++(0.5,0) coordinate(i1)
        to [short, -o] ++(0.5,0) coordinate(x1)
        to [short, i=I] ++(2,0)
        to [R, l={$R_L$}] ++(0,-2)
        to [short, -o] ++(-2,0) coordinate(x2)
        to [short] ++(-1,0)
        to [european voltage source, name={sq}] ++(0,1)
        to [R, l={$R_i$}] (0,0);
    \draw (x1) to [open, v=$U_k$] (x2);
    \draw (sq.north) node[anchor=east](uq){$U_q$};
    %
    \begin{scope}[on background layer]
        \draw[dashed, DARCblue, fill=DARCblue!20](i1)
            -- ++(0,0.25)
            -| (uq.west)
            -- (uq.west|-x2)
            -- ++(0,-0.25) coordinate(h1)
            -- (h1-|i1) coordinate(h2)
            -- (i1);
        \draw(h1) to [open, name={h3}] (h2);
        \draw[DARCblue](h3.center) node[anchor=north]{Reale Spannungsquelle};
    \end{scope} 
\end{circuitikz}