File:Telegrapher equation.gif

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Telegrapher_equation.gif (360 × 256 pixels, file size: 686 KB, MIME type: image/gif, looped, 101 frames)

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Summary

Description
English: The telegrapher's equation describes a signal propagation in a transmission line. If the wires have no resistance and the dielectric separating them is a perfect insulator, it reduces to the wave equation. Otherwise both dispersion and losses are present.
Italiano: L'equazione del telegrafista descrive la propagazione di un segnale in una linea di trasmissione. Se i cavi hanno resistenza zero e il dielettrico che li separa è un isolante perfetto questa si riduce alla semplice equazione delle onde. Altrimenti la soluzione è dispersiva (frequenze diverse si muovono a velocità diverse) ed è presente assorbimento.
Date
Source https://twitter.com/j_bertolotti/status/1172517281374572551
Author Jacopo Bertolotti
Permission
(Reusing this file)
https://twitter.com/j_bertolotti/status/1030470604418428929

Mathematica 11.0 code

(*Find the dispersion relation for the Telegrapher's equation*)
f = E^(I (k x - \[Omega] t));
FullSimplify[D[f, {t, 2}] - v^2 D[f, {x, 2}] + b D[f, t] + c f]

Solve[c + k^2 v^2 + (-I b - \[Omega]) \[Omega] == 0, \[Omega]]

(*Generate the animation*)
\[Sigma] = 1; k0 = 5; b = 0.01; c = 5; v = 1;
g = Sum[(E^(I k x) E^(-(k - k0)^2/(2 \[Sigma]^2)) E^(-I \[Omega] t)) /. {\[Omega] -> k v}, {k, 0, 15, 0.1}];
g2 = Sum[(E^(I k x) E^(-(k - k0)^2/(2 \[Sigma]^2)) E^(-I \[Omega] t)) /. {\[Omega] -> 1/2 (-I b + Abs[Sqrt[-b^2 + 4 c + 4 k^2 v^2]])}, {k, 0, 15, 0.1}];
p1 = Table[
   Show[
    Plot[Re[g], {x, -5, 50}, PlotStyle -> {Orange, Thick}, PlotRange -> {-25, 25}]
    ,
    Plot[Re[g2], {x, -5, 50}, PlotStyle -> {Black, Thick}, PlotRange -> {-25, 25}]
    , Axes -> False, PlotLegends -> {"Wave eq.", "Telegrapher's eq."}
    ]
   , {t, 0, 50, 0.5}];
ListAnimate[p1, 10]

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

Captions

Comparison between the wave and the telegrapher's equations

13 September 2019

image/gif

File history

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Date/TimeThumbnailDimensionsUserComment
current09:56, 16 September 2019Thumbnail for version as of 09:56, 16 September 2019360 × 256 (686 KB)wikimediacommons>BertoUser created page with UploadWizard

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