Parallel of three or more components

Question

I want to draw the circuit in this picture.

I've started with this one:

\begin{circuitikz}
\draw (0,0) to[short,-] ++(6,0) coordinate(a) node[above=0.1cm]{A}
    to[R, l=\mbox{$R_3$}, i>=$I_3$, *-*] ++(0,-6) coordinate(b) node[below=0.1cm]{B}
    to[short,-] ++(-6,0);

.....
.....
.....

\end{circuitikz}

How should I do to add only the parts red marked (e.g. R1, R2, R4 and R5 resistors and so on); they must be at the same height, equal size and symmetrical to R3 resistors (aka, y axis).

Answer 1

You can start, for example, with the following example. The trick is to draw the resistor not between A and B, but from the intermediate horizontal level. A bit of math solves the rest (notice that the math here is for different angles than the one marked in the OP diagram).

I did just one side and manually --- you can clearly use a \foreach loop, but to understand the concept is better to start like this, I think. The other side is left to the reader...

\documentclass[]{article}
\usepackage[siunitx, RPvoltages]{circuitikz}
\begin{document}
\begin{circuitikz}[american]
    % define the gap
    \def\gap{2}
    \draw (0,0) to[short,-] ++(6,0) coordinate(a) node[above=0.1cm]{A}
    % let's mark the heigh h and on the top
    to[short, i=$I_3$] ++(0,-\gap) coordinate(a3)
    to[R, l=\mbox{$R_3$}, *-*] ++(0,-2)
    % and the bottom one
    coordinate(b3)
    to[short] ++(0,-\gap)
    coordinate(b) node[below=0.1cm]{B}
    to[short,-] ++(-6,0);
    % there is surely a more elegant way, but...
    \path (a) ++({-\gap*tan(30)},-\gap) coordinate(a2);
    \draw [color=red] (a) to[short, i_=$I_2$] (a2)
    to[R, l_=$R_2$] (a2|-b3) coordinate(b2)
    to[short] (b);
    \path (a) ++({-\gap*tan(60)},-\gap) coordinate(a1);
    \draw [color=red] (a) to[short, i_=$I_1$] (a1)
    to[R, l_=$R_1$] (a1|-b3) coordinate(b1)
    to[short] (b);
    \draw [ultra thick, line cap=round] (a2) -- (a1) -- ++(-1,0);
    \draw [ultra thick, line cap=round] (b2) -- (b1) -- ++(-1,0);
\end{circuitikz}
\end{document}