Natural Science Forum / Physics / Electromagnetism / March 2006

In a paper "Electrodynamics' spin», I point to a desire of
physicists to deal with a spin density in the electrodynamics. At the
same time, I show that the expression (E x A) is not an electrodynamics
spin density. This expression yields correct results in simplest cases

Hi All, Does anyone happen to know of a paper/website etc. where the
modes in a waveguide of semi-circular cross section is solved for in
terms of Bessel functions? I'm coming across an impasse meeting the
boundary condition on the straight edge. Cheers,

actually i found that when an a.c supply is given to a d.c shunt
motor.the motor fails to run,but when the same supply is given to a d.c
series motor it runs.i couldn't figure out the exact reason behind
this.could you please express your views on this

If two opposing barmagnets would push apart if nothing were between them,
and the same two barmagnets in the same spaced positions would move toward
each other when a soft iron disc were positioned centered between them.  The
soft iron will become magnetised and attract the ...

How does the particle/wave analogy associated with photons apply to radio
waves?
To put it as simply and coherently (no pun intended) as I can, no matter how
I try to interpret radio antenna theory, it always looks to me as though

NEW COSMOLOGICAL MODEL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
"Friedmann-Robertson-Walker" (FRW):::::::::::::::::::::::
dS^2=dt^2.c^2-R(t)^2(dx^2+dy^2+dz^2)
the scale factor for the Universe is

I am studying Stephani et al.'s "Exact Solutions of Einstein's Field
Equations" and had a few question about the Algebraic classifications of the
Energy tensors discussed in Chapter 5, which are still new to me.
Because of the Einstein equations, the Ricci R_uv tensor takes on the ...

Sorry guys.  The spam stuff was not my intent.  I do oppoligies and won't
happen again.  I have never been on newsgroups before and not sure how to
work them. I hope you guys can forgive a bad choice.  Murphey

I want to build an electromagnet, but I don't want it to have any residual
or remanent magnetic field after I drop the current (DC).  It appears that
"soft iron" is the way to go here - it will at least reduce this effect.
Where does one get "soft iron" these days?  Everything I ...

Is there such a thing as a magnetic switch or sensor that would sense
a magnet in the range of 12"-6" away?

Many of the widely-studied solutions to Einstein's field equations are taken
in vacuo, that is, at events where the energy momentum tensor T^uv=0.  This
includes Schwarzchild and Kerr geometries, for example.
Have there been many exact solutions found where T^uv not= 0?  I am ...

hello, I have to evaluate the scattering from a PEC object in free space.
I'm looking for a code, for instance a matlab routine, that implements a 3D
moment method, can you help me? where can i find it?
And what if I want to use a commercial code? which commercial MoM software

Hertz reports wireless transmission in the 1880s.
But, 100 years before Luigi Galvani, while experimenting
with frogs, accidentally discovered that when touching the
nerve of the frog leg with a metal the frog leg would twitch

Tao wrote: >> "FrediFizzx" <fredifizzx@hotmail.com> wrote in message

I wanted to use the concept of Faraday's law to measure strong magnetic
fields emitted from an induction heater (1 kW system)system,  using a
loop of wire and an oscilloscope.
However, I'm facing the following problems: