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<font face="Myriad Pro">Hello Thomas,<br>
<br>
with Manuel's approach and some other idea -- here a possible new way
to get the field lines you presented. The equation for the lines is:<br>
<br>
E_x dy = E_y dx<br>
<br>
using the differential equation features of pstricks-add.<br>
<br>
However this for sure needs some more cosmetics and refinements --
maybe some typing error or whatever.<br>
<br>
Try it out:<br>
<br>
\documentclass{article}<br>
\usepackage{pstricks-add}<br>
<br>
\begin{document}<br>
\begin{pspicture*}(-5,-5)(5,6)<br>
\pstVerb{%<br>
/q1 1 def<br>
/q2 -0.5 q1 mul def<br>
/xA 1.8 def<br>
}<br>
<br>
\multido{\rx=-250+10.2}{50}{%<br>
\psplotDiffEqn[%<br>
linewidth=0.25pt,% <br>
linecolor=red,%<br>
varsteptol=.001,%<br>
method=rk4,%<br>
algebraic,<br>
plotpoints=200%<br>
]{-20}{20}{\rx}{%<br>
(q1*(y[0])/(sqrt((x+xA)^2+(y[0])^2))^3+q2*(y[0])/(sqrt((x-xA)^2+(y[0])^2))^3)%<br>
/%<br>
(q1*(x+xA)/(sqrt((x+xA)^2+(y[0])^2))^3+q2*(x-xA)/(sqrt((x-xA)^2+(y[0])^2))^3)%<br>
}%<br>
}<br>
\pscircle*(!xA 0){0.25}\pscircle*(!xA neg 0){0.25}<br>
\end{pspicture*}<br>
\end{document} <br>
<br>
Regards,<br>
<br>
Juergen<br>
</font><br>
Thomas Söll wrote:
<blockquote cite="mid:890F4103F76741888D98CC4B60EC2A56@BroPC"
type="cite">
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<meta name="GENERATOR" content="MSHTML 8.00.6001.18865">
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<div><font face="Arial" size="2">Hallo Manuel,</font></div>
<div> </div>
<div><font face="Arial" size="2">thank you for your solution. </font></div>
<div> </div>
<div><font face="Arial" size="2">Now I have to understand your way to
find the lines of the field.</font></div>
<div> </div>
<div><font face="Arial" size="2">With best regards,</font></div>
<div> </div>
<div><font face="Arial" size="2">Thomas Söll</font></div>
<blockquote
style="border-left: 2px solid rgb(0, 0, 0); padding-left: 5px; padding-right: 0px; margin-left: 5px; margin-right: 0px;">
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">-----
Original Message ----- </div>
<div
style="background: rgb(228, 228, 228) none repeat scroll 0%; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial;"><b>From:</b>
<a moz-do-not-send="true" title="mluque5130@aol.com"
href="mailto:mluque5130@aol.com">mluque5130@aol.com</a> </div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>To:</b>
<a moz-do-not-send="true" title="pstricks@tug.org"
href="mailto:pstricks@tug.org">pstricks@tug.org</a> </div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Sent:</b>
Sunday, January 17, 2010 10:31 AM</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Subject:</b>
[pstricks] Re : Elektrostatic Field</div>
<div><br>
</div>
<font color="black" face="arial" size="2">
<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>
</div>
<div><font size="2"><font face="Arial, Helvetica, sans-serif"><br>
%%%%%%%%%%%%%%%%%%%%%%<br>
<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>
</font></font></div>
<div><font size="2"><font face="Arial, Helvetica, sans-serif"><br>
Yours sincerely <br>
<br>
Manuel<br>
</font></font></div>
<div><br>
</div>
<div
style="font-family: helvetica,arial; color: black; font-size: 10pt;">-----E-mail
d'origine-----<br>
De : Thomas Söll 1und1 <a class="moz-txt-link-rfc2396E" href="mailto:Thomas.Soell@onlinehome.de"><Thomas.Soell@onlinehome.de></a><br>
A : <a class="moz-txt-link-abbreviated" href="mailto:pstricks@tug.org">pstricks@tug.org</a><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> </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> </div>
<div><font face="Arial" size="2">Has anyone an idea?</font></div>
<div> </div>
<div><font face="Arial" size="2">Thanks for helping.</font></div>
<div> </div>
<div><font face="Arial" size="2">Thomas Söll<img
style="width: 791px; height: 841px;"
src="cid:part1.05010003.04030806@acrotex.net" height="1430"
width="1254"></font></div>
</div>
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