File:Bound currents.gif

Summary

Description
English: If the magnetization in a material is not uniform, the microscopic currents do not cancel, and an overall "bound current" can appear (blue arrows), plus the "surface bound currents" from the unbalanced currents at the surfaces (red arrows).
Date
Source https://twitter.com/j_bertolotti/status/1314868571198107648
Author Jacopo Bertolotti
Permission
(Reusing this file)
https://twitter.com/j_bertolotti/status/1030470604418428929

Mathematica 12.1 code

p0 = Table[
   pts = N@
     Table[0.2 {Cos[\[Theta]], Sin[\[Theta]]}, {\[Theta], 
       0.2 + \[Phi], 2 \[Pi] - 0.2 + \[Phi], (2 \[Pi])/50}];
   m = {0, 0, 1 + x/5};
   Show[
    VectorPlot[
     Evaluate[Curl[m, {x, y, z}][[1 ;; 2]]], {x, 0, 5}, {y, 0, 5}, 
     Frame -> False, PlotRange -> {{-1, 6}, {-1, 6}}, 
     VectorPoints -> 
      Flatten[Table[{i + 0.5, j}, {i, -1, 5}, {j, 0, 5}], 1], 
     VectorStyle -> {Thick, Arrowheads[0.03]}],
    Graphics[{
      Red, Thick, 
      Table[Arrow[{{i - (0.1 + i/10)/2, -0.5}, {i + (0.1 + i/10)/
           2, -0.5}}], {i, 0, 5}],
       Table[
       Arrow[{{i + (0.1 + i/10)/2, 5.5}, {i - (0.1 + i/10)/2, 
          5.5}}], {i, 0, 5}],
       Table[
       Arrow[{{-0.5, i + (0.1 + 0/10)/2}, {-0.5, 
          i - (0.1 + 0/10)/2}}], {i, 0, 5}],
       Table[
       Arrow[{{5.5, i - (0.1 + 5/10)/2}, {5.5, 
          i + (0.1 + 5/10)/2}}], {i, 0, 5}]
      }],
    Graphics[{Thick, 
      Table[Arrow[Plus[{i, j}, #] & /@ ((1 + i/5) pts), 0], {i, 0, 
        5}, {j, 0, 5}]}, PlotRange -> {{-1, 6}, {-1, 6}}]
    ]
   , {\[Phi], 0, 2 \[Pi], (2 \[Pi] - 10^-5)/50}];
ListAnimate[p0]

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.

Category:CC-Zero#Bound%20currents.gifCategory:Self-published work
Category:Magnetization Category:Animations of electromagnetism Category:Images with Mathematica source code Category:Animated GIF files Category:Animations of magnetism
Category:Animated GIF files Category:Animations of electromagnetism Category:Animations of magnetism Category:CC-Zero Category:Images with Mathematica source code Category:Magnetization Category:Self-published work