sci.physics.electromag

On Mar 8, 3:04=A0am, Benj wrote:
> On Mar 7, 7:17 pm, "Timo A. Nieminen" wrote:
>
> > Part the Second
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > The retardation of electromagnetic effects presents a direct challenge t=
o
> > the view of electromagnetism as solely an interaction between charges an=
d
> > currents, with fields merely as a mathematical auxiliary. This is
> > especially the case for radiation.
>
> This is exactly correct! =A0This is what Jefimenko has done in his
> approach and has taken quite a bit of flack for. =A0One problem is that
> a huge amount of problems have been solved using Maxwells equations
> NOT taking retardation into account. =A0People have become so familiar
> with these that they start to assume that these solutions are absolute
> and correct. =A0As you point out, they are not except in certain special
> cases. =A0And this "approximation" thing gets far worse. =A0In practical
> calculations of electromagnetics it's not only common to ignore
> retardation but to ignore a whole host of other problems as well.

Applying the retardation the wrong way can be almost as bad.
Note that the speed of light is allowed for the E field in Maxwell's
equations.

"Retarded potential" (see equation 511)
http://farside.ph.utexas.edu/teaching/em/lectures/node50.html

Nearfield, tunneling or evanecent effects cause the B field
to *appear* faster than light. It isn't really becauese it
diminishes by 1/r^3 and represenst reactive not real power.

The nearfield would be a good place to compare if either the
Maxwell or Jefimenko form gives a better representation
because there is no shortage of people that *think* they
have discovered FTL propagation over magnetic paths.

Sue...



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