Curl of vector fields

The curl of some simple vector fields. Also see the divergence examples, or other figures under the “vectors” tag: the vector sum rule, scalar product, right-hand rule.

Edit and compile if you like:

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% Author: Izaak Neutelings (Februari, 2020)
\documentclass[border=3pt,tikz]{standalone}
\usepackage{amssymb}
\usepackage{physics}
\usepackage{bm}
\usepackage{tikz}
\tikzset{>=latex} % for LaTeX arrow head
\usepackage{xcolor}
\colorlet{veccol}{orange!90!black}
\colorlet{myblue}{blue!60!black}
\tikzstyle{vector}=[->,thick,veccol]
\def\R{1.4}
\def\r{0.03}
\def\N{9}
%\bm{\odot}%otimes
\def\RC{0.14}
\def\Cout{
  \tikz[baseline=-2.5]{ \draw[line width=0.7,myblue] (0,0) circle (\RC);
                        \fill[myblue] (0,0) circle (0.028); }
}
\def\Cin{
  \tikz[baseline=-2.5]{ \draw[line width=0.7,myblue] (0,0) circle (\RC)
                                                     (-135:0.75*\RC) -- (45:0.75*\RC)
                                                     (135:0.75*\RC) -- (-45:0.75*\RC); }
}
\def\null{\color{myblue}{0}}
\begin{document}
% ZERO - solenoid
\begin{tikzpicture}
  \def\ang{60}
  \def\N{6}
  \fill[myblue] (0,0) circle (\r);
  %\foreach \x/\y in {-1/0,-1/1,0/1,1/1,1/0,-1/-1,0/-1,1/-1}{
  %  \draw[vector] (\x*0.5*\R,\y*0.5*\R) --++ (-\y*0.2*\R,\x*0.2*\R);
  %}
  \foreach \R in {0.44,0.88}{
    \foreach \i [evaluate={\ang=\i*360/\N;}] in {1,...,\N}{
      \draw[vector] (\ang:\R) --++ (\ang+90:\R);
 
 
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