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Do two parallel electron beams attract?
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| Here's a variation on the long discussed question of whether or not a
magnetic field rotates with a magnet. Interestingly, people who have
tried experiments to prove that one way or the other have often ALSO
found that DC solenoids as source magnets in their experiments always
seem to give the same results as permanent magnets.
So how about that? Say you had two parallel electron beams where both
had the electrons traveling forward as identical velocities, v. The
usual freshman physics thing is that we have two wires and when the
currents are in the same direction, the wires attract each other. The
idea is that the current in each wire creates a magnetic field at the
other wire which the moving electrons making up the current pass
through. This generates qV X B forces that cause the wires to move
together.
Wires are sort of a complex case due to drift velocities and electrons
bouncing around etc. But two electron beams is straight-forward. Are
two parallel electron beams attracted to each other? If so, this
suggests that when electrons move along the magnetic field is sort of
"peeled off " and left stationary behind them. If the magnetic field
MOVES with the traveling electrons, then clearly the B field generated
about one beam has no relative motion with respect to the second beam
and no attractive qVxB forces can be generated.
Personally, I don't recall ever seeing any "self-focusing" effects
with electron beams of any energy. That seems to imply that the fields
move WITH the electrons which also agrees with the solenoid = perm.
magnet results. This seems like it might be some proof for the age-
old question of whether magnetic fields rotate with a magnet.
What do you guys think? Anybody here have lots of experience with how
electron beams act at various energies?
Benj
| |
| jimp@specsol.spam.sux.com 2007-06-30, 5:25 pm |
| In sci.physics.electromag Benj <bjacoby@iwaynet.net> wrote:
> Here's a variation on the long discussed question of whether or not a
> magnetic field rotates with a magnet. Interestingly, people who have
> tried experiments to prove that one way or the other have often ALSO
> found that DC solenoids as source magnets in their experiments always
> seem to give the same results as permanent magnets.
> So how about that? Say you had two parallel electron beams where both
> had the electrons traveling forward as identical velocities, v. The
> usual freshman physics thing is that we have two wires and when the
> currents are in the same direction, the wires attract each other. The
> idea is that the current in each wire creates a magnetic field at the
> other wire which the moving electrons making up the current pass
> through. This generates qV X B forces that cause the wires to move
> together.
> Wires are sort of a complex case due to drift velocities and electrons
> bouncing around etc. But two electron beams is straight-forward. Are
> two parallel electron beams attracted to each other? If so, this
> suggests that when electrons move along the magnetic field is sort of
> "peeled off " and left stationary behind them. If the magnetic field
> MOVES with the traveling electrons, then clearly the B field generated
> about one beam has no relative motion with respect to the second beam
> and no attractive qVxB forces can be generated.
> Personally, I don't recall ever seeing any "self-focusing" effects
> with electron beams of any energy. That seems to imply that the fields
> move WITH the electrons which also agrees with the solenoid = perm.
> magnet results. This seems like it might be some proof for the age-
> old question of whether magnetic fields rotate with a magnet.
> What do you guys think? Anybody here have lots of experience with how
> electron beams act at various energies?
> Benj
Electron beams left to themselves diverge.
Google cathode ray tube and electrostatic repulsion.
--
Jim Pennino
Remove .spam.sux to reply.
| |
| Salmon Egg 2007-06-30, 5:25 pm |
| On 6/30/07 11:30 AM, in article
1183228257.804465.109450@w5g2000hsg.googlegroups.com, "Benj"
<bjacoby@iwaynet.net> wrote:
> Here's a variation on the long discussed question of whether or not a
> magnetic field rotates with a magnet. Interestingly, people who have
> tried experiments to prove that one way or the other have often ALSO
> found that DC solenoids as source magnets in their experiments always
> seem to give the same results as permanent magnets.
>
> So how about that? Say you had two parallel electron beams where both
> had the electrons traveling forward as identical velocities, v. The
> usual freshman physics thing is that we have two wires and when the
> currents are in the same direction, the wires attract each other. The
> idea is that the current in each wire creates a magnetic field at the
> other wire which the moving electrons making up the current pass
> through. This generates qV X B forces that cause the wires to move
> together.
>
> Wires are sort of a complex case due to drift velocities and electrons
> bouncing around etc. But two electron beams is straight-forward. Are
> two parallel electron beams attracted to each other? If so, this
> suggests that when electrons move along the magnetic field is sort of
> "peeled off " and left stationary behind them. If the magnetic field
> MOVES with the traveling electrons, then clearly the B field generated
> about one beam has no relative motion with respect to the second beam
> and no attractive qVxB forces can be generated.
>
> Personally, I don't recall ever seeing any "self-focusing" effects
> with electron beams of any energy. That seems to imply that the fields
> move WITH the electrons which also agrees with the solenoid = perm.
> magnet results. This seems like it might be some proof for the age-
> old question of whether magnetic fields rotate with a magnet.
>
> What do you guys think? Anybody here have lots of experience with how
> electron beams act at various energies?
>
> Benj
>
The answer is found from the theory of special relativity. First. assume
that all electrons have the same velocity vector. Then, if you are in a
coordinate system with the ame velocity, the electrons appear stationary and
all the electrons repel each other mutually. In that coordinate system,
there is no magnetic field.
If the beams travel at different velocities, assume that you (the coordinate
system) ride along with the slow beam. That slow beam produces no magnetic
field. The other beam does produce a magnetic field. An electron in your
beam sees a force on it that looks like an electric field according to how
the combination of electric and magnetic fields transform under motion.
Bill
--
Iraq: About three Virginia Techs a month
| |
| Spurious Response 2007-06-30, 5:25 pm |
| On Sat, 30 Jun 2007 11:30:57 -0700, Benj <bjacoby@iwaynet.net> wrote:
>Here's a variation...
Like repels.
Inside an X-ray tube, two opposite polarity 90kV DC sources meet
(opposite attracts). A huge electron beam jumps from one node, into the
target element, usually Palladium. Off of that Palladium face splashes a
pretty thick X-ray flux where the electron beam enters the Palladium
target mass.
Pretty cool stuff. Some German Doctor (SGD) ;-] made the one I
described. They run about $950.00 each. About ten inches long and nearly
three inches in diameter. Used in airport X-ray conveyor systems.
180kV Power Supplies is fun stuff to make. :-] X-ray stuff too. Lead
lined cases. Oil filled cases (tanks). We were making one with a brass
case, which also stops X-rays. That would also be oil filled, but end up
slightly lighter than the lead lined solution. Everything sits on thick
G-10 slabs, down in the tank of oil, and has big G-10 blocks and such
used for various construction elements of the supplies. We had a couple
of Delrin bobbins in a couple of the transformer locations.
Want to feel old? When was the last time you looked at a periodic
table? I saw several that I didn't recognize.
http://office.microsoft.com/en-us/t...=CT101446261033
| |
| Salmon Egg 2007-06-30, 9:25 pm |
| I should have also mentioned that many people believe that there is
sufficient residual gas in vacuum tubes so that a plasma of positive ions
builds up around an electron beam to neutralize the electrons. If that is
true, and I have not read any papers to verify it, there will be no dc
forces between electron beams. Positive ions move slowly compared to
electrons. Thus, one can expect electrostatic forces from the fluctuations
of electron density but not from steady state beams.
Bill
| |
| dave y. 2007-06-30, 9:25 pm |
| >The answer is found from the theory of special relativity. First. assume
>that all electrons have the same velocity vector. Then, if you are in a
>coordinate system with the ame velocity, the electrons appear stationary and
>all the electrons repel each other mutually. In that coordinate system,
>there is no magnetic field.
....
>Bill
Interesting. So, if I understand this correctly, if we have two
observers, one moving at the same velocity as the electron and the
other moving at a different velocity, then the first observer doesn't
see a magnetic field, but the second one does. In fact, in the first
case there actually isn't a magnetic field, but in the second case
there is one.
This makes my head hurt. Is this right? How could this be...?
Once the field is generated, doesn't it propagate on it's own
independent of what its source electron is doing? And independent of
what any particular observer is doing?...
Ouch, it hurts again.
| |
| jimp@specsol.spam.sux.com 2007-06-30, 9:25 pm |
| In sci.physics.electromag Salmon Egg <salmonegg@sbcglobal.net> wrote:
> I should have also mentioned that many people believe that there is
> sufficient residual gas in vacuum tubes so that a plasma of positive ions
> builds up around an electron beam to neutralize the electrons. If that is
> true, and I have not read any papers to verify it, there will be no dc
> forces between electron beams. Positive ions move slowly compared to
> electrons. Thus, one can expect electrostatic forces from the fluctuations
> of electron density but not from steady state beams.
Many people believe Elvis is alive.
Both "theories" are equally dumb.
--
Jim Pennino
Remove .spam.sux to reply.
| |
|
|
j...@specsol.spam.sux.com wrote:
> In sci.physics.electromag Salmon Egg <salmonegg@sbcglobal.net> wrote:
>
> Many people believe Elvis is alive.
>
> Both "theories" are equally dumb.
I don't know how "dumb" these theories are but I verify that the first
one isn't correct. In Freshman physics lab there was this experiment
we all did. It was to measure e/m for electrons. I forget the details
but an electron beam was accelerated into an almost evacuated bulb
which was placed between a pair of Helmholtz coils. The idea was that
when you adjusted the magnetic field and the acceleration voltage just
right the beam made a perfect circle back to it's starting point and
you could calculate e/m from that.
OK. But all that isn't the point. The point is that we were told that
the bulb was not totally evacuated so that there was sufficient
residual gas in the bulb so that a plasma of positive ions built up
around the electron beam. (remind you of anything?) In this case the
purpose was so you could see the electron beam in the dark from the
ionization. I can say for sure that this beam very definitely got
wider and more fuzzy as it proceeded through the tube. Clearly there
WERE DC forces defocusing the beam. I suppose one could argue it was
collisions with ions doing it, but I don't think there was a great
density in the tube.
As for Elvis.... I swear I saw him over at a Burger King near here...
MAN, did he look OLD! :-)
| |
|
|
Salmon Egg wrote:
>
> The answer is found from the theory of special relativity. First. assume
> that all electrons have the same velocity vector. Then, if you are in a
> coordinate system with the same velocity, the electrons appear stationary and
> all the electrons repel each other mutually. In that coordinate system,
> there is no magnetic field.
OK. That makes sense. So let me ask you this. I've seen it said on a
number of websites discussing the issue of whether or not a magnetic
field rotates with a magnet that according to Einstein, a magnetic
field MUST rotate with the magnet for SR to be correct. Your above
argument seems to say the same thing in that if the magnetic field did
NOT travel with the electron then in the moving coordinate system
there WOULD be a magnetic field because it would have a velocity
different from the electrons. Do you think this is what they meant
when they say a magnetic field must rotate with the magnet according
to SR?
Benj
| |
| Salmon Egg 2007-07-01, 9:25 am |
| On 6/30/07 6:52 PM, in article 4g1e831me8bf1achjirutso7vgggmph1mf@4ax.com,
"dave y." <nospam@myhouse.com> wrote:
> ...
>
>
> Interesting. So, if I understand this correctly, if we have two
> observers, one moving at the same velocity as the electron and the
> other moving at a different velocity, then the first observer doesn't
> see a magnetic field, but the second one does. In fact, in the first
> case there actually isn't a magnetic field, but in the second case
> there is one.
>
> This makes my head hurt. Is this right? How could this be...?
> Once the field is generated, doesn't it propagate on it's own
> independent of what its source electron is doing? And independent of
> what any particular observer is doing?...
>
> Ouch, it hurts again.
>
>
It may make your head hurt, but you are getting it.
It turns out that there is a tensor (maybe a new buzz word for you) that is
a combination of the electric and magnetic fields called the electromagnetic
field. This tensor is an invariant. That is, it is an entity that represents
the EM field that does not change as you look at it in from various
"laboratories" moving at various uniform velocities. It is analogous to
representing a vector by its x, y, and z components. If you look at a vector
from a rotated coordinate system, it still is the same vector, but the x, y,
and z components have changed.
In a moving coordinate system, the EM field is the same, but the various
measured electric field and magnetic field components describing the fields
have been changed the same way as the x, y, and z components of an unchanged
vector have changed in a rotating coordinate system.
Another place tensors show up is in stress and strain. The stress tensor is
a combination of shear and tensile stress, depending upon how you pick a
coordinate system.
These days, EEs probably learn more about tensors and how to use them than
they used to. In my day, tensors were left to mathematicians. Engineers got
a poor man's version of tensor analysis for stress and strain by using
Mohr's circle to show how materials could fail in tension when undergoing
tensile stress.
Bill
--
Iraq: About three Virginia Techs a month
| |
| Salmon Egg 2007-07-01, 9:25 am |
| On 6/30/07 10:20 PM, in article
1183267214.024668.155730@c77g2000hse.googlegroups.com, "Benj"
<bjacoby@iwaynet.net> wrote:
> OK. That makes sense. So let me ask you this. I've seen it said on a
> number of websites discussing the issue of whether or not a magnetic
> field rotates with a magnet that according to Einstein, a magnetic
> field MUST rotate with the magnet for SR to be correct. Your above
> argument seems to say the same thing in that if the magnetic field did
> NOT travel with the electron then in the moving coordinate system
> there WOULD be a magnetic field because it would have a velocity
> different from the electrons. Do you think this is what they meant
> when they say a magnetic field must rotate with the magnet according
> to SR?
I fail to follow your logic as to why the magnetic field, say of long
cylindrical magnet rotates if you rotate the magnet along the cylindrical
axis. In fact, experiment has shown that the field does not rotate with the
magnet. It does not induce an emf in a loop of wire connected to the ends of
the magnet with a conducting brush.
Bill
--
Iraq: About three Virginia Techs a month
| |
| maxwell 2007-07-01, 1:25 pm |
| On Jun 30, 6:52 pm, dave y. <nos...@myhouse.com> wrote:
> ...
>
> Interesting. So, if I understand this correctly, if we have two
> observers, one moving at the same velocity as the electron and the
> other moving at a different velocity, then the first observer doesn't
> see a magnetic field, but the second one does. In fact, in the first
> case there actually isn't a magnetic field, but in the second case
> there is one.
>
> This makes my head hurt. Is this right? How could this be...?
> Once the field is generated, doesn't it propagate on it's own
> independent of what its source electron is doing? And independent of
> what any particular observer is doing?...
>
> Ouch, it hurts again.
This is the kind of confused thinking that arises from the invention
of mathematical intermediaries that are then considered real, such as
E & M "fields". There are only electrons & they move relative to each
other. Work out the problem in terms of charges & potentials (see C.
J. Carpenter) & determine the observable motion - all the rest is just
math.
| |
| jimp@specsol.spam.sux.com 2007-07-01, 1:25 pm |
| In sci.physics.electromag Benj <bjacoby@iwaynet.net> wrote:
> j...@specsol.spam.sux.com wrote:
[color=darkred]
> I don't know how "dumb" these theories are but I verify that the first
> one isn't correct. In Freshman physics lab there was this experiment
> we all did. It was to measure e/m for electrons. I forget the details
> but an electron beam was accelerated into an almost evacuated bulb
> which was placed between a pair of Helmholtz coils. The idea was that
> when you adjusted the magnetic field and the acceleration voltage just
> right the beam made a perfect circle back to it's starting point and
> you could calculate e/m from that.
> OK. But all that isn't the point. The point is that we were told that
> the bulb was not totally evacuated so that there was sufficient
> residual gas in the bulb so that a plasma of positive ions built up
> around the electron beam. (remind you of anything?) In this case the
> purpose was so you could see the electron beam in the dark from the
> ionization. I can say for sure that this beam very definitely got
> wider and more fuzzy as it proceeded through the tube. Clearly there
> WERE DC forces defocusing the beam. I suppose one could argue it was
> collisions with ions doing it, but I don't think there was a great
> density in the tube.
> As for Elvis.... I swear I saw him over at a Burger King near here...
> MAN, did he look OLD! :-)
A few points:
The term "vacuum tubes" has a specific meaning. A vacuum tube with
gas in it (other than say mercury vapor rectifiers) is a failed tube.
Anything that gets in the path of a stream will diverge the stream.
Vegetation will diverge a stream of machine gun bullets. Electron
streams are not exempt.
--
Jim Pennino
Remove .spam.sux to reply.
| |
| srp@microtec.net 2007-07-01, 1:25 pm |
| On 30 juin, 14:30, Benj <bjac...@iwaynet.net> wrote:
> Here's a variation on the long discussed question of whether or not a
> magnetic field rotates with a magnet. Interestingly, people who have
> tried experiments to prove that one way or the other have often ALSO
> found that DC solenoids as source magnets in their experiments always
> seem to give the same results as permanent magnets.
>
> So how about that? Say you had two parallel electron beams where both
> had the electrons traveling forward as identical velocities, v. The
> usual freshman physics thing is that we have two wires and when the
> currents are in the same direction, the wires attract each other. The
> idea is that the current in each wire creates a magnetic field at the
> other wire which the moving electrons making up the current pass
> through. This generates qV X B forces that cause the wires to move
> together.
>
> Wires are sort of a complex case due to drift velocities and electrons
> bouncing around etc. But two electron beams is straight-forward. Are
> two parallel electron beams attracted to each other?
This question is doomed to remain hypothetical, since there seems
to exist no set up allowing to focus two separate parallel electron
beams withing the same guiding E and B fields.
If you calibrate your fields to have an electron stream to be
correctly
focussed, then you can have only one beam in the fields.
Ref: "Principles of Charged Particle Acceleration", Wiley & Sons,
by S. Humphries.
Andr=E9 Michaud
| |
| Salmon Egg 2007-07-01, 1:25 pm |
| On 7/1/07 9:04 AM, in article
1183305848.024699.36770@d30g2000prg.googlegroups.com, "maxwell"
<spsi@shaw.ca> wrote:
> This is the kind of confused thinking that arises from the invention
> of mathematical intermediaries that are then considered real, such as
> E & M "fields". There are only electrons & they move relative to each
> other. Work out the problem in terms of charges & potentials (see C.
> J. Carpenter) & determine the observable motion - all the rest is just
> math.
Do you mean that there are no entities such as protons, neutrons, molecules,
ions, etc?
Observations leading to the theory of relativity were being made before and
during the establishment of the existence of electrons. Maxwell had no
knowledge of the existence of electrons. Nevertheless, his equations fitted
in very well with the theory of relativity when it was expounded. Faraday
himself noted that there was something wron with understanding when induced
emf in coils of wire did not depend upon whether the coil was moved or
whether the magnet was moved.
There is good reason for relying on "just math' if you understand what you
are doing. Mathematical physics is not an exercise of picking equations out
of your mathematical cookbook.
Bill
-- Support the troops. Impeach Bush. Oh, I forgot about Cheney.
| |
| Salmon Egg 2007-07-01, 1:25 pm |
| On 7/1/07 9:05 AM, in article hevkl4-6t7.ln1@mail.specsol.com,
"jimp@specsol.spam.sux.com" <jimp@specsol.spam.sux.com> wrote:
> A few points:
>
> The term "vacuum tubes" has a specific meaning. A vacuum tube with
> gas in it (other than say mercury vapor rectifiers) is a failed tube.
>
> Anything that gets in the path of a stream will diverge the stream.
> Vegetation will diverge a stream of machine gun bullets. Electron
> streams are not exempt.
Let's see. A mole of air is about 6E23 molecules in a volume of 24200 cc. A
really good vacuum would be 1E-9torr. That is about 1E-12 atmosphere
pressure. If I do my arithmetic correctly that is about 25 million molecules
of air per mL (cubic centimeter). Hardly a perfect vacuum.
Remember however, for engineering purposes, good enough is perfect.
Bill
--
Iraq: About three Virginia Techs a month
| |
| jimp@specsol.spam.sux.com 2007-07-01, 1:25 pm |
| In sci.physics.electromag Salmon Egg <salmonegg@sbcglobal.net> wrote:
> On 7/1/07 9:05 AM, in article hevkl4-6t7.ln1@mail.specsol.com,
> "jimp@specsol.spam.sux.com" <jimp@specsol.spam.sux.com> wrote:
[color=darkred]
> Let's see. A mole of air is about 6E23 molecules in a volume of 24200 cc. A
> really good vacuum would be 1E-9torr. That is about 1E-12 atmosphere
> pressure. If I do my arithmetic correctly that is about 25 million molecules
> of air per mL (cubic centimeter). Hardly a perfect vacuum.
Which is why tubes have getters.
> Remember however, for engineering purposes, good enough is perfect.
True.
--
Jim Pennino
Remove .spam.sux to reply.
| |
|
|
Salmon Egg wrote:
>
> I fail to follow your logic as to why the magnetic field, say of long
> cylindrical magnet rotates if you rotate the magnet along the cylindrical
> axis.
My logic would be that if a magnetic field moves with an electron at a
certain velocity (which the electron beam considerations seem to show)
then doesn't it follow that a magnet made up of charged particles and
generating a magnetic field from say circulating currents of some kind
would of necessity move with the charged particles giving rise to the
the permanent field?
> In fact, experiment has shown that the field does not rotate with the
> magnet. It does not induce an emf in a loop of wire connected to the ends of
> the magnet with a conducting brush.
I think this is the big argument! Because a rotating magnet doesn't
induce emf in a coil (or Faraday generator disk) people have assumed
that the field does not rotate. But then another group of people
answer that, no, the first group failed to consider the induced emf in
the WIRING which cancels the emf in the disk so it only "appears" that
there is no emf generated. People looking at this have concluded that
nobody seems to have come up with an experiment that definitively
shows which of these two alternatives is the correct one and the
argument seems to rage on.
What I therefore asked was to go back a step to first principles and
ask if a magnetic field moves with an electron (idea came from data
that said that one gets the same results from a permanent magnet as
you do from rotating a coil of wire). We seem to agree here that the
field MUST move with the electron (other wise e-beams would self-focus
and magnetic fields would appear out of nowhere in a reference frame
attached to the electrons).
So I don't think that anyone has really settled the question (Raging
since the days of Faraday) of whether the magnetic field rotates.
Seems to me like someone ought to be clever enough to find an
experimental arrangement that could separate the effects of induction
in the test loop from that in the wiring. Apparently nobody has. The
last was A.G. Kelly of Ireland who thought he'd shown proof that the
field rotates with the magnet, but then others tore apart his data
showing that once again BOTH explanations (Field rotates or field does
not rotate) gave identical results in his setup. (Nice list of
references on the topic at end)
Benj
| |
|
| On Jul 1, 2:28 am, Salmon Egg <salmon...@sbcglobal.net> wrote:
> On 6/30/07 6:52 PM, in article 4g1e831me8bf1achjirutso7vgggmph...@4ax.com,
>
>
>
>
>
> "dave y." <nos...@myhouse.com> wrote:
>
>
>
>
> It may make your head hurt, but you are getting it.
>
> It turns out that there is a tensor (maybe a new buzz word for you) that is
> a combination of the electric and magnetic fields called the electromagnetic
> field. This tensor is an invariant. That is, it is an entity that represents
> the EM field that does not change as you look at it in from various
> "laboratories" moving at various uniform velocities. It is analogous to
> representing a vector by its x, y, and z components. If you look at a vector
> from a rotated coordinate system, it still is the same vector, but the x, y,
> and z components have changed.
>
> In a moving coordinate system, the EM field is the same, but the various
> measured electric field and magnetic field components describing the fields
> have been changed the same way as the x, y, and z components of an unchanged
> vector have changed in a rotating coordinate system.
>
> Another place tensors show up is in stress and strain. The stress tensor is
> a combination of shear and tensile stress, depending upon how you pick a
> coordinate system.
>
> These days, EEs probably learn more about tensors and how to use them than
> they used to. In my day, tensors were left to mathematicians. Engineers got
> a poor man's version of tensor analysis for stress and strain by using
> Mohr's circle to show how materials could fail in tension when undergoing
> tensile stress.
I could kind of handle tensors, at least in a vague sense as to how
the explanation you give here works, but when the physics instructor
brought up spinors, I changed majors.
| |
|
| On Jul 1, 12:04 pm, maxwell <s...@shaw.ca> wrote:
> This is the kind of confused thinking that arises from the invention
> of mathematical intermediaries that are then considered real, such as
> E & M "fields". There are only electrons & they move relative to each
> other. Work out the problem in terms of charges & potentials (see C.
> J. Carpenter) & determine the observable motion - all the rest is just
> math.-
But can you explain magnetism without relativistic effects, or do you
just have to accept it as a given and do the math? You certainly can't
"explain" it in terms of charges and potentials.
| |
| Szczepan Bialek 2007-07-11, 5:25 pm |
|
"Benj" <bjacoby@iwaynet.net> wrote
news:1183228257.804465.109450@w5g2000hsg.googlegroups.com...
> Here's a variation on the long discussed question of whether or not a
> magnetic field rotates with a magnet. Interestingly, people who have
> tried experiments to prove that one way or the other have often ALSO
> found that DC solenoids as source magnets in their experiments always
> seem to give the same results as permanent magnets.
>
> So how about that? Say you had two parallel electron beams where both
> had the electrons traveling forward as identical velocities, v. The
> usual freshman physics thing is that we have two wires and when the
> currents are in the same direction, the wires attract each other. The
> idea is that the current in each wire creates a magnetic field at the
> other wire which the moving electrons making up the current pass
> through. This generates qV X B forces that cause the wires to move
> together.
>
> Wires are sort of a complex case due to drift velocities and electrons
> bouncing around etc. But two electron beams is straight-forward. Are
> two parallel electron beams attracted to each other? If so, this
> suggests that when electrons move along the magnetic field is sort of
> "peeled off " and left stationary behind them. If the magnetic field
> MOVES with the traveling electrons, then clearly the B field generated
> about one beam has no relative motion with respect to the second beam
> and no attractive qVxB forces can be generated.
>
> Personally, I don't recall ever seeing any "self-focusing" effects
> with electron beams of any energy.
What do you think about this: http://en.wikipedia.org/wiki/Z-pinch
That seems to imply that the fields
> move WITH the electrons which also agrees with the solenoid = perm.
> magnet results. This seems like it might be some proof for the age-
> old question of whether magnetic fields rotate with a magnet.
>
> What do you guys think? Anybody here have lots of experience with how
> electron beams act at various energies?
Plasma contains electron beams.
S*
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Szczepan Bialek wrote:
> "Benj" <bjacoby@iwaynet.net> wrote
>
> What do you think about this: http://en.wikipedia.org/wiki/Z-pinch
> Plasma contains electron beams.
Um. Yes! I had forgotten about Z-pinch in plasmas. Obviously there is
something going on here that needs some thought. The current in a
plasma actually DOES produce a self-focusing effect! Of course it's
not particularly stable much to the dismay of the early fusion people,
but that is of no consequence to the discussion here.
So what we observe so far seems to be:
1. electrons in a beam do NOT self-focus. This implies that the
magnetic field is moving with the electrons so that a reference frame
attached to the electrons won't see any anomalous magnetic fields
arising from electrons that appear to be at rest.
2. A MIXTURE of positive (ions) and negative (electrons) in a plasma
DO self-focus. This somehow implies that the magnetic field generated
by current through the plasma is able to act back upon that plasma to
compress it.
3. A MIXTURE of positive (protons) and negative (electrons) charges in
a WIRE also are able to create a magnetic field which apparently is
not moving at the velocity of the basic charged particles. If wires
were like hollow tubes which electrons fired down then wires carrying
current would NOT attract! As it is, we know that electrons in metals
are bouncing around in there like mad and only move forward with a
drift velocity. Somehow this fact allows magnetic motional forces to
exist between the wires. And indeed I believe that there are observed
"self-focusing" effects of a sort which is the current distributions
found in heavy current DC bus bars due to the internal magnetic
fields.
Therefore it seems to me that there are two situations here. One is
the pure case of electron beams and the other are the cases of charged
particles bouncing around in a mix in plasmas and inside wires.
Methinks there could be some fundamental physics here!
Good point, Szczepan!
Benj
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"Benj" <bjacoby@iwaynet.net> wrote in message
news:1183389354.399047.11XXXX@k79g2000hse.googlegroups.com...
>
> Salmon Egg wrote:
cylindrical[color=darkred]
>
> My logic would be that if a magnetic field moves with an electron at a
> certain velocity (which the electron beam considerations seem to show)
> then doesn't it follow that a magnet made up of charged particles and
> generating a magnetic field from say circulating currents of some kind
> would of necessity move with the charged particles giving rise to the
> the permanent field?
>
ends of[color=darkred]
>
> I think this is the big argument! Because a rotating magnet doesn't
> induce emf in a coil (or Faraday generator disk) people have assumed
> that the field does not rotate. But then another group of people
> answer that, no, the first group failed to consider the induced emf in
> the WIRING which cancels the emf in the disk so it only "appears" that
> there is no emf generated. People looking at this have concluded that
> nobody seems to have come up with an experiment that definitively
> shows which of these two alternatives is the correct one and the
> argument seems to rage on.
>
> What I therefore asked was to go back a step to first principles and
> ask if a magnetic field moves with an electron (idea came from data
> that said that one gets the same results from a permanent magnet as
> you do from rotating a coil of wire). We seem to agree here that the
> field MUST move with the electron (other wise e-beams would self-focus
> and magnetic fields would appear out of nowhere in a reference frame
> attached to the electrons).
>
> So I don't think that anyone has really settled the question (Raging
> since the days of Faraday) of whether the magnetic field rotates.
> Seems to me like someone ought to be clever enough to find an
> experimental arrangement that could separate the effects of induction
> in the test loop from that in the wiring. Apparently nobody has. The
> last was A.G. Kelly of Ireland who thought he'd shown proof that the
> field rotates with the magnet, but then others tore apart his data
> showing that once again BOTH explanations (Field rotates or field does
> not rotate) gave identical results in his setup. (Nice list of
> references on the topic at end)
>
> Benj
>
>Interesting question - If you spin a bar magnet on its lengthwise axis
(pole to pole), does its magnetic field also spin?
We cannot observe effects of induction from the spinning field.
Answer, A barmagnet has a magnetic field from pole to pole. This is a
wysiwyg approach with much observible action at a distance phenomina. BUT
lets explore the magnet a bit. he magnet has more attributes than a magnetic
field. Ampere tells us it has an electrical field which is tangential to the
bar and as you view the magnet, the clockwise or ccw direction of the
electrical field is the determination of whether we view the north or south
magnetic pole. The classical experiment
of placing a barmagnet near a crt screen and observing effects on the cxrt
electron beam clearly demonstrates his point
and shows how any charged partical in motion has its inertia redirected by
the Amperian dynamic electrical field. A simple case of the charged partical
seeking a path of least resistance. In this scenerio there is no magnetic
field, and it is not observed, however The Amperian dynamic electrical field
is shown to be capable of action at a distance.
When magnets attract or repell it is this re-direction of inertia of the
magnets responding to each others Amperian dynamic electrical field which we
think of as a contiguous force but it doesnot span the gap, only the
Amperian dynamic electrical field
spans the gap.
If you spin the bar magnet and try to observe induction, you cannot because
you are really spinning the Amperian dynamic electrical field which is
already tangentially aligned but radially propagated in a avalanch
propagation.
While two magnetics use redirection of inertia as a cause and effect
mechanism, Curved Amperian dynamic electrical fields are employed.
Redirection of inertia is also the mechanism of gravitation but without the
curving of the Amperian dynamic electrical field. Kind regards, Lee Pugh
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| Szczepan Bialek 2007-07-12, 5:25 pm |
|
Uzytkownik "Benj" <bjacoby@iwaynet.net> napisal w wiadomosci
news:1184207562.318969.181410@n2g2000hse.googlegroups.com...
>
> Szczepan Bialek wrote:
>
>
> Um. Yes! I had forgotten about Z-pinch in plasmas. Obviously there is
> something going on here that needs some thought. The current in a
> plasma actually DOES produce a self-focusing effect! Of course it's
> not particularly stable much to the dismay of the early fusion people,
> but that is of no consequence to the discussion here.
>
> So what we observe so far seems to be:
>
> 1. electrons in a beam do NOT self-focus. This implies that the
> magnetic field is moving with the electrons so that a reference frame
> attached to the electrons won't see any anomalous magnetic fields
> arising from electrons that appear to be at rest.
It seems that electrons in a beam behave according to the current density.
See the pages 18 and 19 (Alfven current) of::
http://deposit.ddb.de/cgi-bin/dokse...e=972318054.pdf
>
> 2. A MIXTURE of positive (ions) and negative (electrons) in a plasma
> DO self-focus. This somehow implies that the magnetic field generated
> by current through the plasma is able to act back upon that plasma to
> compress it.
It should be also density dependent.
>
> 3. A MIXTURE of positive (protons) and negative (electrons) charges in
> a WIRE also are able to create a magnetic field which apparently is
> not moving at the velocity of the basic charged particles. If wires
> were like hollow tubes which electrons fired down then wires carrying
> current would NOT attract! As it is, we know that electrons in metals
> are bouncing around in there like mad and only move forward with a
> drift velocity. Somehow this fact allows magnetic motional forces to
> exist between the wires. And indeed I believe that there are observed
> "self-focusing" effects of a sort which is the current distributions
> found in heavy current DC bus bars due to the internal magnetic
> fields.
".. heavy current DC" = The current density which give a noticeable effect.
>
> Therefore it seems to me that there are two situations here. One is
> the pure case of electron beams and the other are the cases of charged
> particles bouncing around in a mix in plasmas and inside wires.
> Methinks there could be some fundamental physics here!
>
> Good point, Szczepan!
I try to be constructive.
S*
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