btr
Registered Member
Perhaps they have an anti-spam measure against posts with links from relatively new users.
I PM'd one of the Admins; that was precisely the issue (I'd quoted a post with a link in it).
Perhaps they have an anti-spam measure against posts with links from relatively new users.
Farsight won't be returning to this thread, unfortunately, so I've taken the liberty of following up on my own request from a few pages back, on the subject of the spiral diagram:
Here is what you get if you literally add a radial inverse-square electric field to a dipole magnetic field, in the spirit of the spiral diagram from earlier:
View attachment 7092
Code:StreamPlot[{x/(x^2 + y^2)^(3/2) + x*y/(x^2 + y^2)^(5/2), y/(x^2 + y^2)^(3/2) + ((2/3)*y^2 - (1/3)*x^2)/(x^2 + y^2)^(5/2)}, {x, -1, 1}, {y, -1, 1}]
To be clear, I don't claim that this has any useful meaning. Adding E to B makes no physical sense, and immediately loses half of the data at each point in space. There is no way to calculate forces on particles from the combined field any more (neither magnitude nor direction), nor can you predict the future evolution of the fields given the current value and rate of change of the combined field at each point. As a result, combining the two fields with this sort of strategy cannot faithfully represent the true electromagnetic field.
Features of the combined field:
- At large distances, the dipole component is negligible in comparison with the inverse square component, and approximate spherical symmetry is seen in the combined field. The system looks very like an ordinary point source at this range.
- At intermediate distances, the combined field begins to deviate markedly from spherical symmetry. It still has rotational symmetry about the dipole axis, however.
- At very close distances, the dipole component dominates. On the dipole axis, the field still points away from the source (and its magnitude varies approximately as the inverse cube of the distance); however, in the horizontal plane, the field points "downwards" instead of away from the source.
- As you approach the dipole along its axis from "below" the horizontal plane, there is a point where the field actually changes direction from outwards to inwards! In the attached plot, that happens at (x, y) = (0, -2/3).
Farsight won't be returning to this thread, unfortunately, so I've taken the liberty of following up on my own request from a few pages back, on the subject of the spiral diagram:
Oh truly feel sorry about that. For some guys you are not willing to discuss or debate with, we can leave them alone and continue your valued debates.That's why we're all gradually leaving this forum.