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<div> <font size="2"><font face="Arial, Helvetica, sans-serif">This example draws only the vectors at selected points.<br>
If nobody gives a complete solution to trace the lines of electric field, I think I can do it in 2 or 3 weeks...</font></font><br>
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<br>
\documentclass{article}<br>
\usepackage{pstricks,multido}<br>
\SpecialCoor<br>
\def\fieldlines{% <br>
/xP \nx\space def<br>
/yP \ny\space def<br>
/r1 xP xA sub dup mul yP dup mul add sqrt def<br>
/r2 xP xA add dup mul yP dup mul add sqrt def<br>
% /V q1 r1 div<br>
% q2 r2 div<br>
% add def<br>
% Ex=-dV/dx<br>
/Ex q1 xP xA sub mul r1 3 exp div<br>
q2 xP xA add mul r2 3 exp div<br>
add def<br>
% Ey=-dV/dy<br>
/Ey yP <br>
q1 r1 3 exp div<br>
q2 r2 3 exp div<br>
add mul def<br>
/NormeE Ex dup mul Ey dup mul add sqrt def<br>
/uEx Ex NormeE div K mul def<br>
/uEy Ey NormeE div K mul def<br>
}<br>
\begin{document}<br>
<br>
\begin{pspicture}(-5,-5)(5,6)<br>
\multido{\nx=-5+0.5}{22}{%<br>
\multido{\ny=-5+0.5}{22}{%<br>
\pstVerb{/q1 1 def<br>
/q2 -0.5 q1 mul def<br>
/K 1 def<br>
/xA 1.8 def<br>
\fieldlines}<br>
\rput(\nx,\ny){\psline{->}(0,0)(!uEx uEy)\psdot(0,0)}<br>
}}<br>
\pscircle*(!xA 0){0.25}\pscircle*(!xA neg 0){0.25}<br>
\end{pspicture}<br>
<br>
\begin{pspicture}(-5,-5)(5,6)<br>
\multido{\nx=-5+0.5}{22}{%<br>
\multido{\ny=-5+0.5}{22}{%<br>
\pstVerb{/q1 -1 def<br>
/q2 2 q1 mul def<br>
/K 1 def<br>
/xA 2.2 def<br>
\fieldlines}<br>
\rput(\nx,\ny){\psline{->}(0,0)(!uEx uEy)\psdot(0,0)}<br>
}}<br>
\pscircle*(!xA 0){0.25}\pscircle*(!xA neg 0){0.25}<br>
\end{pspicture}<br>
\end{document}<br>
<br>
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>
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<div> <font size="2"><font face="Arial, Helvetica, sans-serif"><br>
Yours sincerely <br>
<br>
Manuel<br>
</font></font></div>
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<div style="font-family: helvetica,arial; font-size: 10pt; color: black;">-----E-mail d'origine-----<br>
De : Thomas Söll 1und1 <Thomas.Soell@onlinehome.de><br>
A : pstricks@tug.org<br>
Envoyé le : Samedi, 16 Janvier 2010 15:02<br>
Sujet : [pstricks] Elektrostatic Field<br>
<br>
<div id="AOLMsgPart_4_af1f1b42-2be3-4245-8931-87be65f6282b">
<div><font face="Arial" size="2">Hallo,</font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">is it possible to draw the the lines of an
E-Field from the superposition of two radialsymmetric Charges, as in the
picture drawn.</font></div>
<div><font face="Arial" size="2">There is one +Q1, the other -0,5*Q1.</font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">Has anyone an idea?</font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">Thanks for helping.</font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">Thomas Söll<img style="width: 791px; height: 841px;" src="cid:059DAA4B403842C0B1B5EDF2338FBAC1@BroPC" height="1430" width="1254"></font></div>
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