+ Post New Thread
Results 1 to 10 of 10

13th February 2018, 17:49 #1
 Join Date
 May 2010
 Location
 Poland
 Posts
 231
 Helped
 5 / 5
 Points
 2,874
 Level
 12
Maxwell's equations  is there a bigger picture?
Maxwell's Equations sometimes are satisfied and sometimes are not satisfied. Examples:
1) Gauss' Law can be violated e.g. by a Gaussian beam of EM waves.
2) Ampere's law leads to the equation
grad(div(B))  Δ (B) = mu0*eps0*(d^2 B/dt^2) which is violated and then
the wave equation: Δ(B) = mu0*eps0*(d^2 B/dt^2) is satisfied.
Do you have any idea why?

Advertisment

15th February 2018, 16:32 #2
 Join Date
 Jun 2012
 Location
 Edmonton, Canada
 Posts
 1,021
 Helped
 295 / 295
 Points
 6,627
 Level
 19
Re: Maxwell's equations  is there a bigger picture?
Maxwell's equations are always satisfied.
Do people's assumptions agree with Maxwell's equations? Not always.
2 members found this post helpful.

23rd February 2018, 19:12 #3
 Join Date
 May 2010
 Location
 Poland
 Posts
 231
 Helped
 5 / 5
 Points
 2,874
 Level
 12
Electrodynamics, wave equation, velocity of waves
1) div(B)=0 and div(E)=0 are true only in magnetostatic and electrostatic situations, otherwise they can be violated (consider a Gaussian beam of EM waves).
2) Maxwell's extension of the Ampere's Law is completely false (Otherwise magnetically longitudinal, electrically torsional waves could not propagate e.g. in a ferrite rod or toroid).
As a result, Wave Equation cannot be derived from true laws of Electrodynamics.
My question:
Is it possible to predict the phase velocity of a magnetically longitudinal, electrically torsional wave in a ferrite characterized by (epsr, mur) ?

23rd February 2018, 23:53 #4
 Join Date
 May 2010
 Location
 Poland
 Posts
 231
 Helped
 5 / 5
 Points
 2,874
 Level
 12
Re: Maxwell's equations  is there a bigger picture?
I give clear examples where Maxwell's equations are violated.
Maxwell's equations are supposed to be valid in any situation which can
be encountered in Electrodynamics. There are no hidden assumptions.
So take it into account if you are going to post a reply.

Advertisment

24th February 2018, 07:29 #5
 Join Date
 Apr 2011
 Location
 Minneapolis, Minnesota, USA
 Posts
 12,649
 Helped
 2516 / 2516
 Points
 51,537
 Level
 55

24th February 2018, 15:47 #6
 Join Date
 May 2010
 Location
 Poland
 Posts
 231
 Helped
 5 / 5
 Points
 2,874
 Level
 12

25th February 2018, 04:22 #7
 Join Date
 Apr 2011
 Location
 Minneapolis, Minnesota, USA
 Posts
 12,649
 Helped
 2516 / 2516
 Points
 51,537
 Level
 55
Re: Electrodynamics, wave equation, velocity of waves
No doubt you're correct in some regards, but as I understand it, electromagnetic waves are of a different nature than a magnetic field. We can listen to radio broadcasts because the antenna shoots photons, rather than growing and collapsing a magnetic field. So my radio detects photons from a long distance, and need not be within the circle of the antenna's magnetic influence.
Unlike magnetic waves, radio waves (electromagnetic or EM waves):
* bounce off the ionosphere, can go around the world,
* reflect off buildings and airplanes (multipath),
* are directional when broadcast by a suitable antenna (satellites, microwave towers),
etc.
Magnetic fields show a different kind of behavior, although they have a sort of directionality. I haven't memorized all the equations nor similarities or differences. Perhaps it's easy for people to think they're the same phenomenon because they share the word 'magnetic' in their names?

25th February 2018, 12:32 #8
 Join Date
 May 2010
 Location
 Poland
 Posts
 231
 Helped
 5 / 5
 Points
 2,874
 Level
 12
Re: Electrodynamics, wave equation, velocity of waves

Advertisment

6th June 2018, 05:46 #9
 Join Date
 May 2018
 Posts
 2
 Helped
 0 / 0
 Points
 31
 Level
 1
Re: Electrodynamics, wave equation, velocity of waves
So my radio detects photons from a long distance, and need not be within the circle of the antenna's magnetic influence.

6th August 2018, 20:41 #10
 Join Date
 Aug 2018
 Posts
 6
 Helped
 0 / 0
 Points
 39
 Level
 1
Re: Maxwell's equations  is there a bigger picture?
+ Post New Thread
Please login