% Prof. Dr. Matthias Jung, DL9MJ
% 2024
\begin{circuitikz}
    \draw(0,0) -- ++(3,0);
    \fill[DARCred!50] (3,-1) rectangle ++(2,2);
    \fill[DARCblue!30](5,-1) rectangle ++(2,2);
    \draw(3,-1) rectangle ++(2,2);
    \draw(5,-1) rectangle ++(2,2);
    \draw(7,0) -- ++(3,0);
    \draw (4,1.5) node[](){\Large P};
    \draw (6,1.5) node[](){\Large N};
    \draw(0,0)
        to [short] ++(0,-2.5)
        to [short, i<={\textcolor{DARCred}{tech.}}] ++(3.33333,0)
        to [battery2, v>={$U$}] ++(3.33333,0)
        to [short, i>={\textcolor{DARCblue}{phys.}}] ++(3.33333,0)
        to [short] ++(0,+2.5);
\end{circuitikz}