%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  7. Auflage
%% 
%%  Beispiel 32-03-61 auf Seite 760.
%% 
%%  Copyright (C) 2016 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{193.16928pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{pst-electricfield}
%StopShownPreambleCommands
\begin{document}
\begin{pspicture*}(-10,-5)(6,5)
  \psgrid[subgriddiv=0,gridcolor=lightgray,griddots=10]
  \psElectricfield[Q={[600 -60 0 false][-4 0 0] },N=50,points=500,runit=0.8]
  \psEquipotential[Q={[600 -60 0 false][-4 0 0]},linecolor=blue,Vmax=100,
    Vmin=50,stepV=2](-10,-5)(6,5)
  \psframe*(-10,-5)(-9.5,5)
  \rput(0,0){\textcolor{white}{\large$-$}}
  \multido{\rA=4.75+-0.5}{20}{\rput(-9.75,\rA){\textcolor{white}{\large$+$}}}
\end{pspicture*}
\end{document}