# [pstricks] Re : Elektrostatic Field

Thomas Söll Thomas.Soell at lehrer.uka.de
Sun Jan 17 16:01:22 CET 2010

Hallo Manuel,

Now I have to understand your way to find the lines of the field.

With best regards,

Thomas Söll
----- Original Message -----
From: mluque5130 at aol.com
To: pstricks at tug.org
Sent: Sunday, January 17, 2010 10:31 AM
Subject: [pstricks] Re : Elektrostatic Field

This example draws only the vectors at selected points.
If nobody gives a complete solution to trace the lines of electric field, I think I can do it in 2 or 3 weeks...

%%%%%%%%%%%%%%%%%%%%%%

\documentclass{article}
\usepackage{pstricks,multido}
\SpecialCoor
\def\fieldlines{%
/xP \nx\space def
/yP \ny\space def
/r1 xP xA sub dup mul yP dup mul add sqrt def
/r2 xP xA add dup mul yP dup mul add sqrt def
%        /V q1 r1 div
%           q2 r2 div
%        Ex=-dV/dx
/Ex q1 xP xA sub mul r1 3 exp div
q2 xP xA add mul r2 3 exp div
%        Ey=-dV/dy
/Ey yP
q1 r1 3 exp div
q2 r2 3 exp div
/NormeE Ex dup mul Ey dup mul add sqrt def
/uEx Ex NormeE div K mul def
/uEy Ey NormeE div K mul def
}
\begin{document}

\begin{pspicture}(-5,-5)(5,6)
\multido{\nx=-5+0.5}{22}{%
\multido{\ny=-5+0.5}{22}{%
\pstVerb{/q1 1 def
/q2 -0.5 q1 mul def
/K 1 def
/xA 1.8 def
\fieldlines}
\rput(\nx,\ny){\psline{->}(0,0)(!uEx uEy)\psdot(0,0)}
}}
\pscircle*(!xA 0){0.25}\pscircle*(!xA neg 0){0.25}
\end{pspicture}

\begin{pspicture}(-5,-5)(5,6)
\multido{\nx=-5+0.5}{22}{%
\multido{\ny=-5+0.5}{22}{%
\pstVerb{/q1 -1 def
/q2 2 q1 mul def
/K 1 def
/xA 2.2 def
\fieldlines}
\rput(\nx,\ny){\psline{->}(0,0)(!uEx uEy)\psdot(0,0)}
}}
\pscircle*(!xA 0){0.25}\pscircle*(!xA neg 0){0.25}
\end{pspicture}
\end{document}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Yours sincerely

Manuel

-----E-mail d'origine-----
De : Thomas Söll 1und1 <Thomas.Soell at onlinehome.de>
A : pstricks at tug.org
Envoyé le : Samedi, 16 Janvier 2010 15:02
Sujet : [pstricks] Elektrostatic Field

Hallo,

is it possible to draw the the lines of an E-Field from the superposition of two radialsymmetric Charges, as in the picture drawn.
There is one +Q1, the other -0,5*Q1.

Has anyone an idea?

Thanks for helping.

Thomas Söll
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