"Edward Green" <spamspamspam3@[EMAIL PROTECTED]
> wrote in message
news:2c4f7726-3eea-42b1-a482-6715baf52bfc@[EMAIL PROTECTED]
Jun 3, 2:55 pm, "Neil B." <neil_del...@[EMAIL PROTECTED]
> wrote:
[I have to put quotes since my ">" isn't working, even though I checked it
in the Options tab - can you imagine why?]
"Want to try again? Your ascii-digramless description wasn't entirely
clear to me. :-) You have a line source electric field, and you have
a current loop in a plane containing the line. OK so far? I'm not
sure why you need a pair of current loops to express your problem."
You've got the picture right. I use a pair of loops to cancel out some of
the effects they have on the wire.
"You move the current loop in and out, always in the plane containing
the line source, and you claim somehow we have an inexplicable
variation in L -- angular momentum.
Since you don't mind typing, would you answer some stupid questions?
(1) What is L measured about in this context? (e.g., a perpedicular
in the center of the current loop?)"
No, keep it at the same place: in the "middle" of the line charge imposed
on the x axis. Call the ref. point the origin of coordinates, and the
loops are centered on the y axis.
"(2) What explicit form of L gives you the variation -- i.e., what "p"
are you integrating via r x p which you claim paradoxically varies?"
OK, since p = mv, then dL/dt = m dv/dt + v dm/dt. It is easy to forget
about the latter term since net mass-energy usually can't grow inside of
something. However, it can, as when an electric field pushes charges along
and they do work accordingly. Yet I am not imagining a conventional
current of electrons, but many tiny charges that are literally pushed
along by the current on one side, and need to be pushed against the
current on the other side. That dm/dt term is what keeps the L growing,
since r and dm/dt are opposite sign on opposite sides, but v is the same
for both as we move the solenoids away. That gives the same net.
"(3) Are you talking about an electrically neutral current loop, or a
rotating ring of charge?"
Make it neutral.
"I'm not sure I see the "cryptic" angular momentum (though I do see the
spider lowering itself from the pipe above me), but if it's there, I
am guessing that by pu****ng charge around you are conveniently
radiating away any unaccounted for angular momentum."
See and work on above explanations to find the extra L. There is likely an
answer, but isn't radiation from simply pu****ng the charges around - a
continuous train of charges in stable motion doesn't radiate (the current
in this case is constant magnitude, a fixed value of equivalent current.)
I think the angular momentum is given back if we ever do change the
current in the solenoids, by the electric induction fields (see my final
reply to "Puppet_Sock." But note that it could be a long time before we do
that. IOW, angular momentum can be stored in fields and be like potential
energy. Most paradoxes like this have some solution based on interchanges
between "mechanical" quantities and "field" quantities.
Thanks for your interest.
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