🚀 go-pugleaf

"Sergey Karavashkin" <selftrans@yandex.ru> wrote in message
news:a42650fc.0401191437.384c3447@posting.google.com...
> "Harry" <harald.vanlintel@epfl.ch> wrote in message
news:<4003ff4f$1@epflnews.epfl.ch>...
> > "Bilge" <dubious@radioactivex.lebesque-al.net> wrote in message
> > news:slrnc06a45.8e.dubious@radioactivex.lebesque-al.net...
> > > Harry:
> > >  >
> > >  >"Bilge" <dubious@radioactivex.lebesque-al.net> wrote in message
> > >  >news:slrnbvraov.dan.dubious@radioactivex.lebesque-al.net...
> >
> > >  >>   The motion of a charge next to a wire can be found in a fairly
> > >  >> straight-forward way just by finding the B-field from the wire and
> > >  >> and using the lorentz force law. (Working in the frame in which
the
> > >  >> field from the wire is purely magnetic).
> > >  >
> > >  >True. So now we have:
> > >  >
> > >  >�
> > >  >�  very long wire
> > >  >�
> > >  >�     <- -  o+    charged object , v<<c
> > >  >�
> > >  >�
> > >  >^
> > >  >Thus: I can see that the object is pushed downward, and, if I'm not
> > >  >mistaken, that the wire is pushed counter clock wise.
> > >
> > >    The field of a long wire is just given in MKSA by
> > >
> > > B = \mu_0 I_enc/(2pi r)
> > >
> > >    (in the \phi direction using cylindrical coordinates)
> > >
> > >   The force comes from the lorentz force law, F = qv x B, so if the
> > > motion of the charge is along the radial direction, the direction
> > > of the force is along z. Balancing the forces requires the force
> > > on the wire to be along z.
> > >
> > >  >In order for the forces to balance I miss an upward longitudinal
force
> >  on
> > >  >the wire.
> > >
> > >   That would be an induced current from the motion of the charge,
> > >
> > > curl B = j + dE/dt.
> >
> > That doesn't really do, or does it?! I find no change of flux inside any
> > wire loop, if we extend the picture to a large wire loop, and even if
there
> > was, a current does not directly equal a force.
> > I still see nothing else but the magnetic field coming from the moving
> > charge, resulting in curl B ~ dE/dt. And I already concluded that the
> > resulting Lorentz forces on the nearby wire elements provide a counter
clock
> > turning moment (which is also needed for complete force balance), but
the
> > upward force is lacking...
> >
> > >  It should also be clear that currents in wires cannot be treated
> > > as moving charges using maxwell's equations without additional
> > > assumptions about the wire which requires quantum mechanics to
> > > explain. The charges would repel each other if they were not
> > > bound to the wire by a mechanism beyond the ability of maxwell's
> > > equations to explain.
> >
> > Ye. Still, explanation of how a wire functions is irrelevant for this
> > problem.
> >
> > > [...]
> > >  >>  >Sorry, perhaps Ampere had several laws?!
> > >  >>  >I meant the Ampere force law, which is very roughly:
> > >  >>  >
> > >  >>  >F = -i_m * i_n *(dm . dn / r^2) * (2 cos phi - 3 cos a cos b)
> > >  >>
> > >  >>   I didn't realize ampere had a "force law" other than what could
> > >  >> be derived from the usual equations. In any case, that expression
> > >  >> is written in a particular frame (which is okay). But, notice that
> > >  >> because it's derived under the assumption of infinitely long
wires,
> > >  >> it's rather unphysical (at least from a relativistic standpoint),
> > >  >> since the current can't ever begin flowing or stop flowing, but
> > >  >> had to have existed and continue to exist for all time.
> > >  >
> > >  >In fact, no such assumption was made, it describes the force between
two
> > >  >individual charge elements.
> > >
> > >   Yes, such an assumption _is_ made because the integral of ampere's
> > > law, curl B = j, is a line integral over a closed path. Writing that
> > > as current elements, is a convenient fiction which requires evaluating
> > > the line integral over the entire _closed_ path. For a straight wire
> > > (or any other wire which is not explicitly closed) the path is closed
> > > at infinity.
> >
> > Yes - or not really at infinity, and integrating all the relevant parts.
In
> > this case, one does not have to extend very far to reach sufficient
> > accuracy.
> >
> > >  The biot-savart law is just a vector identity that allows you to
> > > write an integral for B under the assumption that dl is a closed
> > > path. I'm also not sure I understand the geometry of the wires for
> > > which that force equation is derived. The angles \phi, a and b refer
> > > to some assumption about the relative orientation of the configration.
> >
> > Sorry, when I wrote it I did not put an effort in it, just wanted to
> > identify the law. It's a bit complex to describe, and I haven't played
with
> > it myself. Phi is the angle between the current flow directions of each
> > element, and alpha and beta are the angle of each current flow direction
> > with the line between the current elements.
> >
> > > [...]
> > >
> > >  >Perhaps it's a paying website, sorry. My university has subscription
on
> >  a
> > >  >number of them...
> > >  >It's IEEE trans. on Plasma Science, vol.21, no.6, dec.1993, pp.
701-713.
> > >  >N. Graneau, "An electrodynamic vacuum arc ion acceleration mechanism
> >  based
> > >  >on Ampere's force law".
> > >
> > >   Plasmas are very messy and approximations abound. I would assume
that
> > > the article makes several either implicitly or explicitly.
> >
> > Yes, obviously. Main point is that this paper also claims that the laws
do
> > make different predictions, with the Ampere force law more in agreement
with
> > observations than the Lorentz force law, and that the Ampere force law
has
> > "balanced action and reaction".
> >
> > Harald
>
>
> Dear Harald,
>
> Long time I tried to catch from your discussion with Bilge, what
> concern has the Ampere's law to my respond to Leo! And only now I
> began understanding. This relates not to my respond to Leo but to our
> experiments on induction with which you disagreed and remained the
> standpoint of loop phenomenology of induction. And now you are
> attempting to find the way, how to explain this through the Ampere's
> law, i.e., through the interaction of two conductors with the current.
>
> But first, you will not be able to manage it. You know, when I say so.
> ;-)
>
> Second, to find efficiently the branching in existing formulas, one
> has to be not mistaken in his reasoning. In particular, you wrote
> about the paper attractive for you:
>
> [Harald]
> Main point is that this paper also claims that the laws do
> make different predictions, with the Ampere force law more in
> agreement with
> observations than the Lorentz force law, and that the Ampere force law
> has
> "balanced action and reaction".
>
> [Sergey]
> Don't you think that you can derive the Lorentz force equation on the
> basis of Ampere's law? ;-) Further, what it means in the Lorentz law
> not "balanced action and reaction"? Balance of action and
> counter-action is determined by the model. In the Lorentz law the idea
> of magnetic field is used, but if you in your model consider not only
> affection of this field on the moving charge but also reaction of the
> charge to the source of magnetic field, this all will become balanced.
>
> Thus, have a pleasant "disagreement". ;-)
>
> Sergey

Sergey,
In fact we were on a side subject, after I tried to make clear that being
open-minded is not the same as being a crackpot..
Ampere's law is more complete than Lorentz', and seems to be not fully
compatible with Maxwell's.
Just when I expected Bilge to actually show me that all forces are balanced
due to something that I overlooked, he became silent.
What is according to you the reaction of a current carrying wire to a moving
charge?

Harald