# Draw field lines through a circle

I need to drawn field's line through a spherical superconductor and normal conductor, like this image: but i never drew in Latex befor and i don't know how i can do that. Someone can help me?

• welcome to tex.se. for star see tikz or pstrick examples.for the first one look in texample.net. without showing anything what you try so far, your question is do-this-for-me, which likely will not be answered. – Zarko Sep 18 '17 at 1:33
• You may get an answer, but I recommend including a duck in your target image as people like drawing those. But you may not, without code, if your image isn't very interesting or challenging. (And it is just a couple of circles and some lines, basically, so interest and challenge are going to be on the low side.) A duck would look good in the blue ponds. However, you may find people get distracted and forget to draw the rest of it in that case. But you could always decide to draw a duck instead - then you'd have the best of both worlds. – cfr Sep 18 '17 at 1:56
• I have made this drawing before in some lecture notes of mine. (screenshot, code line 12-40) – Henri Menke Sep 18 '17 at 3:12
• @HenriMenke You should post this as an answer. – Andrew Sep 18 '17 at 6:51
• @JohnKormylo It doesn't strictly have to be a duck, but ducks seem especially popular around here, don't you think? A cat would be a good choice, too, if ducks are really not an option. – cfr Sep 18 '17 at 12:47

With solving the implicit defined equation. Run with pdflatex --shell-escape

\documentclass[pstricks]{standalone}
\usepackage{pst-func}
\usepackage{auto-pst-pdf}
\begin{document}

\begin{pspicture*}(-5,-2.5)(5.5,3.5)
\pscircle(0,0){1}%
%\psaxes{->}(0,0)(-5,-2)(5.2,3)%
\multido{\rA=0.01+0.2}{5}{%
\psplotImp[linewidth=1pt,linecolor=blue,polarplot,
stepFactor=0.2,algebraic](-6,-6)(6,2.4){%
(r^2-1/r)*(sin(phi/57.296)^2)-\rA}}%
\uput*(0,2){$f(r,\phi)=\left(r^2-\frac{1}{r}\right)\cdot\sin^2\phi=0$}
\psline[arrowscale=2,linewidth=1.5pt,linecolor=black!40]{->}(-4,-1.5)(4,-1.5)
\end{pspicture*}

\end{document} 