Example: Daniell’s pile

% Daniell's Pile
% Author: Agustin E. Bolzan
\documentclass{article}
\usepackage{tikz}
\begin{document}

\definecolor{copper}{cmyk}{0,0.9,0.9,0.2}
\colorlet{lightgray}{black!25}
\colorlet{darkgray}{black!75}

\centering
\Large {Daniell's Pile}
\vspace{2cm}


\begin{tikzpicture}
    % Draw back of vessel 1
    \draw (0,0) to [controls=+(90:0.5) and +(90:0.5)] (2,0);
    \draw[fill=blue!60, fill opacity=0.5] (0,-0.5) to
        [controls=+(90:0.5) and +(90:0.5)] (2,-0.5);

    % Draw back of vessel 2
    \draw (3.5,0) to [controls=+(90:0.5) and +(90:0.5)] (5.5,0);
    \draw[fill=lightgray, fill opacity=0.5] (3.5,-0.5) to [controls=+(90:0.5)
        and +(90:0.5)] (5.5,-0.5);

    % Draw copper electrode
    \draw[fill=copper] (0.5,2) rectangle (1.5,-1);
    \draw (0,2.3) node {Cu};
    \draw (1,-1.75) node {\small{CuSO$_{4}$}};

    % Draw salt bridge

    \draw[join=round, line width = 10pt] (1.75,-1.75) -- (1.75,0.5) --
        (3.75, 0.5) -- (3.75,-1.75);
    \draw[join=round, line width = 5pt, color = gray!25] (1.75,-1.75) --
        (1.75,0.5) -- (3.75, 0.5) -- (3.75,-1.75);
    \draw (2.75,0.5) node {\tiny{KNO$_{3}$}};

    %Draw front of vessel 1

    \draw (0,0) .. controls +(-90:0.5) and +(-90:0.5) .. (2,0);
    \draw (0,0) .. controls +(-90:0.5) and +(-90:0.5) .. (2,0)
        -- (2,-0.5) .. controls +(-90:0.5) and +(-90:0.5) .. (0,-0.5) -- (0,0);

    %Second part

    \draw[fill=blue!60, fill opacity=0.5] (0,-0.5) .. controls +(-90:0.5)
    and +(-90:0.5) .. (2,-0.5);
    \draw[fill=blue!60, fill opacity=0.5] (0,-0.5) .. controls +(-90:0.5)
    and +(-90:0.5) .. (2,-0.5)
        -- (2,-2) .. controls +(-90:0.5) and +(-90:0.5) .. (0,-2) -- (0,-0.5);

    % draw voltmeter

    \draw[join = round, thick] (1,2) -- (1,2.5) -- (4.5,2.5) -- (4.5,2);
    \draw (2.75,2.5) node [circle, draw, fill=red!30] {V};

    %Draw back of vessel 2

    %Draw electrode

    \draw[fill=darkgray] (4,2) rectangle (5,-1);
    \draw (5.5,2.3) node {Zn};
    \draw (4.5,-1.75) node {\small{ZnSO$_{4}$}};

    % Draw front of vessel 2
    % part 1
    \draw (3.5,0) .. controls +(-90:0.5) and +(-90:0.5) .. (5.5,0);
    \draw (3.5,0) .. controls +(-90:0.5) and +(-90:0.5) .. (5.5,0)
        -- (5.5,-0.5) .. controls +(-90:0.5) and +(-90:0.5)
        .. (3.5,-0.5) -- (3.5,0);
    % part 2
    \draw[fill=lightgray, fill opacity=0.5] (3.5,-0.5) .. controls +(-90:0.5)
    and +(-90:0.5) .. (5.5,-0.5);
    \draw[fill=lightgray, fill opacity=0.5] (3.5,-0.5) .. controls +(-90:0.5)
        and +(-90:0.5) .. (5.5,-0.5) --
        (5.5,-2) .. controls +(-90:0.5) and +(-90:0.5)
        .. (3.5,-2) -- (3.5,-0.5);

\end{tikzpicture}


\end{document}