Draw picture of electric transformer

Question

I would like to draw an electric transformer close to this image

Ideally there would be more spires on one side than the other

I had learned to do some tree decision with Tikz, so I can do two concentric circles, but I do not have any idea how to do the rest. I put a MWE (I have several math related packages that I omitted, I hope these are sufficient to compile it) to show I have done something even if it is not a lot.

\documentclass[a4paper]{book}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}    
\usepackage{amsmath, amsthm, amssymb}
\usepackage{mathtools}
\usepackage{tikz-cd}
\usetikzlibrary{shapes,arrows,intersections}
\usetikzlibrary{matrix,fit,calc,trees,positioning,arrows,chains,shapes.geometric,shapes}


\begin{document}

\begin{figure}[htp]
\caption{Un transformateur}
\begin{tikzpicture}
\centering
    \node[circle,draw,inner sep=1.2cm,label={[font=\bfseries]}] (b) at (7,0) {};
    \node[circle,draw,inner sep=1.5cm,label={[font=\bfseries]+80:Tore en matériau ferromagnétique}] (c) at (7,0) {};
\end{tikzpicture}
\end{figure}
\end{document

I am open to another package than Tikz if judged more appropriat.

I have found this thread with impressive 3D transformers, but first I do not understand most of what is done and second it takes too much time to compile for the online compiler I use.

Thx

Answer 1

I believe that the following code can work as a starting point for you. Adjust all the dimensions as needed, and add decorations and labels as in your picture. Note that the coil is straight and does not follow the curve of the ring. To make it work, you need the mypathmorphing code from this answer: Modify TikZ coil decoration

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.mypathmorphing}
\begin{document}
\begin{tikzpicture}
\draw (-8,1.5) -- (-4.5,1.5);
\draw [decorate, decoration={coilup, aspect=0.4, amplitude=7 mm,  segment length=3mm}]   (-4.5,1.5) -- (-4.5,-1.5);
\draw [decorate, decoration={coildown, aspect=0.4, amplitude=7 mm,  segment length=2mm}] (4.5,-1.5) -- (4.5,1.5);
\draw (4.5,1.5) -- (8,1.5);
\draw [fill=white, even odd rule] (0,0) circle (5cm) (0,0) circle (4cm);
\draw [decorate, decoration={coilup, aspect=0.4, amplitude=7 mm,  segment length=2mm}]   (4.5,-1.5) -- (4.5,1.5);
\draw [decorate, decoration={coildown, aspect=0.4, amplitude=7 mm,  segment length=3mm}] (-4.5,1.5) -- (-4.5,-1.5);
\draw (-8,-1.5) -- (-4.5,-1.5);
\draw (4.5,-1.5) -- (8,-1.5);
\end{tikzpicture}
\end{document}