Magnetic lines of force

In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

-- Jeff, in Minneapolis

..

On 19 Aug 2003 18:46:30 -0700, (Jeff Root) wrote:

In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

-- Jeff, in Minneapolis

There are no lines of force that manifest themselves physically in time
and space. It is just a dumb term for magnetic field that someone
invented when watching the lines of clumped iron filings. This has
confused many people. Just ask yourself what is between two lines of
force or can you have a one half line of force.

--

Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/
Aurora, Ontario

In article , Boris Mohar
wrote:

On 19 Aug 2003 18:46:30 -0700, (Jeff Root) wrote:

In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

-- Jeff, in Minneapolis

There are no lines of force that manifest themselves physically in
time and space.

Really? Then there would be no such thing as flux, either, eh?
(neither magnetic nor electric).

It is just a dumb term for magnetic field that someone invented
when watching the lines of clumped iron filings.

And then a magnetic 'field' would be just dumb term someone invented
also, eh? After all, we can't really legitimately suppose that it is a
continuous structure because it only appears where there is matter or
some measuring apparatus. We have no data that suggests it might be at
places we haven't placed something akin to an instrument.


This has confused many people. Just ask yourself what is between
two lines of force or can you have a one half line of force.

Maybe you're the person who is confused. Perhaps you suppose that a
magnetic 'field' is a continuous structure. Perhaps that's your
religion? I mean, after all, it is only a belief and not something
that you can demonstrate by any experiment.

Maybe you can't grasp or manage to form a proper model in your mind
where the so called 'field' of, say, an elementary charged particle is
composed of a finite number of discrete subcomponents? Perhaps that's
your problem, Boris. No sight and no insight.

Charles Cagle

On Tue, 02 Sep 2003 01:59:17 GMT, CC wrote:

In article , Boris Mohar
wrote:

On 19 Aug 2003 18:46:30 -0700, (Jeff Root) wrote:

In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

-- Jeff, in Minneapolis

There are no lines of force that manifest themselves physically in
time and space.

Really? Then there would be no such thing as flux, either, eh?
(neither magnetic nor electric).

It is just a dumb term for magnetic field that someone invented
when watching the lines of clumped iron filings.

And then a magnetic 'field' would be just dumb term someone invented
also, eh? After all, we can't really legitimately suppose that it is a
continuous structure because it only appears where there is matter or
some measuring apparatus. We have no data that suggests it might be at
places we haven't placed something akin to an instrument.


This has confused many people. Just ask yourself what is between
two lines of force or can you have a one half line of force.

Maybe you're the person who is confused. Perhaps you suppose that a
magnetic 'field' is a continuous structure. Perhaps that's your
religion? I mean, after all, it is only a belief and not something
that you can demonstrate by any experiment.

Maybe you can't grasp or manage to form a proper model in your mind
where the so called 'field' of, say, an elementary charged particle is
composed of a finite number of discrete subcomponents? Perhaps that's
your problem, Boris. No sight and no insight.

Charles Cagle

Nobody spreads as much darkness as one who has seen the light


--

Boris Mohar

In article , Boris Mohar
wrote:

On Tue, 02 Sep 2003 01:59:17 GMT, CC wrote:

In article , Boris Mohar
wrote:

On 19 Aug 2003 18:46:30 -0700, (Jeff Root) wrote:

In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

-- Jeff, in Minneapolis

There are no lines of force that manifest themselves physically in
time and space.

Really? Then there would be no such thing as flux, either, eh?
(neither magnetic nor electric).

It is just a dumb term for magnetic field that someone invented
when watching the lines of clumped iron filings.

And then a magnetic 'field' would be just dumb term someone invented
also, eh? After all, we can't really legitimately suppose that it is a
continuous structure because it only appears where there is matter or
some measuring apparatus. We have no data that suggests it might be at
places we haven't placed something akin to an instrument.


This has confused many people. Just ask yourself what is between
two lines of force or can you have a one half line of force.

Maybe you're the person who is confused. Perhaps you suppose that a
magnetic 'field' is a continuous structure. Perhaps that's your
religion? I mean, after all, it is only a belief and not something
that you can demonstrate by any experiment.

Maybe you can't grasp or manage to form a proper model in your mind
where the so called 'field' of, say, an elementary charged particle is
composed of a finite number of discrete subcomponents? Perhaps that's
your problem, Boris. No sight and no insight.

Charles Cagle

Nobody spreads as much darkness as one who has seen the light

Nonsense. Being a creature of darkness you've given every indication
that you're unable to see light.

CC

Jeff Root wrote in message
om...
In another thread, George Dishman explained:

I think you understand my point of view here, that 'x' and 'y'
are conceptual while the paper that holds the dots apart is real.

Could you apply this same kind of wonderfully clear exegesis to
the term "magnetic lines of force"? I keep seeing intimations
that they have some kind of reality. Thank you!

Magnetic lines of force were first described by Faraday. (Faraday,
"Experimental Researches")

And yes, they do have 'some kind of reality'. Sprinkle iron filings on a
sheet of paper, then bring a strong magnet around. Always the same pattern
at a given distance and orientation.

Maxwell developed 'Maxwell's equations' and first identified light as
transverse electromagnetic waves in a paper titled "On Physical Lines of
Force", 1861. Based -- in part -- on Faraday's work. Maxwell also produced
an earlier paper:
Cambridge Philosophical Transactions, vol. x. part 1. art. 3, "On Faraday's
Lines of Force."


greywolf42
ubi dubium ibi libertas

"greywolf42" wrote in message
...

George Dishman wrote in message
...

"greywolf42" wrote in message
...

And yes, they do have 'some kind of reality'. Sprinkle iron filings
on a
sheet of paper, then bring a strong magnet around. Always the same
pattern
at a given distance and orientation.

At any point in space the field has a strength and direction.
Suppose you mark where the lines lie on the paper with a pen
then remove the filings and carefully measure the field strength

a) on a line

b) between lines

Would the strength in (a) be greater than that in (b)?

Place a single filing on the paper and glue it down so it doesn't
fly off to the magnet. It creates an easier path for the field to
flow along in its immediate vicinity than passing through the air
so it distorts the field nearby and causes an increase of field
strength near the tips.

Well, yes. You've added another 'source' into the field, due to magnetic
induction (also noticed by Faraday and derived by Maxwell). However, the
'power' of that source is a function of the first magnet, and it's
distance.

I don't disagree with any of that. You have added
useful detail to my explanation of the mechanism.

It is a small effect but if a second filing
is placed nearby, it will be drawn to the first by the increased
local strength again shortening the path length and reinforcing
the effect.

If you let all the filings move equally, you won't get the above
distortion.

It gets more complex when considering 'all' but
just two illustrates the mechanism as I understand
it.

If you just 'drop' that first filing in place, it will always go to one of
the same lines that were traced out prior, or afterwards.

There I disagree. If you drop a single filing it
will always attach itself to the magnet if it is
free enough to move. Obviously friction usually
stops it.

There is nothing special about any location around the
magnet, the line will form in the direction of the field from
wherever you choose to fix the first filing.

That's because you've 'cheated' and arbitrarily 'glued' the 'first'
someplace other than a normal line-of-force. This creates a second
(interfering) source in the combined magnetic fields.

If you were correct, the filings would remain stationary when you move the
magnet along, underneath the paper. Yet still they move. (Try it.)

Once you have a chain of filings from one pole to
the other, attempting to move the magnet without
moving the filings would create a gap and all the
force is concentrated there. That is enough to
overcome the friction.

Going back to two filings with the first glued,
moving the magnet will not usually cause the
second to move but to rotate to remain aligned
with the field while still remaining in contact
with the first. (Try it ;-)

More scientifically, suppose we have this
arrangement:

N
|
| f --
|
S

--x--

A single filing is held at 'f' and the force
plotted against the distance 'x' from the magnet
as the filing is moved along a line perpendicular
to the axis. If you were right then there should
be a cyclical variation since the force should
have maxima when the filing is on a line and
minima in-between. This is not the case.

George

When I've played with iron filings and magnets in the past,
the effect of friction between the filings and paper has always
seemed obvious. I'm not sure that I would learn anything from
using a low-friction surface instead (what seemed obvious might
not even be real), but I'll try it if I can. Do you have any
suggestions for a low-friction material to put between the
filings and the magnet?

Hmm. Low friction means the filings are going to slide off
and get into the carpet. I'll just have to pick them up again
with the magnet.

The shape of the filings is obviously significant. Do you have
any suggestions for getting filings which are nearly spherical,
and which are not themselves magnetized? Maybe a particular
kind of iron or steel?

Just now I filed a nail with two different sizes of file. The
bigger, slightly coarser file gave bigger filings, but it isn't
clear that the size and shape distribution is different.

One thing that *is* very different: I put twice as much time
and effort in with the smaller file, and got 1/10th the amount
of filings. I need a vise to hold the nail. I need a workbench
to hold the vise. I need a workroom to hold the bench. I need
a house to hold the workroom. I can't afford a vise.

I'm answering my own questions. I made the filings onto a hard
plastic tray from the kitchen. It seems to have lower friction
than some paper. When I apply a magnet, the itty-bitty little
filings climb up on each other's shoulders to do a flea-circus
stunt where they make relatively huge needles (compared to the
size of the filings) which stand up from the tray surface.

-- Jeff, in Minneapolis

..

"Jeff Root" bravely wrote to "All" (09 Sep 03 16:47:11)
--- on the heady topic of " Magnetic lines of force"

JR From: (Jeff Root)

JR When I've played with iron filings and magnets in the past,
JR the effect of friction between the filings and paper has always
JR seemed obvious. I'm not sure that I would learn anything from
JR using a low-friction surface instead (what seemed obvious might
JR not even be real), but I'll try it if I can. Do you have any
JR suggestions for a low-friction material to put between the
JR filings and the magnet?

Yes try to place the iron filings in a bottle filled with oil or water.
Then shake it so they are all in suspension then try your magnets.

Asimov
******

.... Diagonally parked in a parallel universe.

"Jeff Root" wrote in message
om...
When I've played with iron filings and magnets in the past,
the effect of friction between the filings and paper has always
seemed obvious. I'm not sure that I would learn anything from
using a low-friction surface instead (what seemed obvious might
not even be real),

No, but greywolf42 might ;-)

but I'll try it if I can. Do you have any
suggestions for a low-friction material to put between the
filings and the magnet?

PTFE (Teflon) would be good, but you seem to have solved
that below. You can float the filings on water using
surface tension but that can make stick by itself.

Hmm. Low friction means the filings are going to slide off
and get into the carpet. I'll just have to pick them up again
with the magnet.

The shape of the filings is obviously significant. Do you have
any suggestions for getting filings which are nearly spherical,
and which are not themselves magnetized? Maybe a particular
kind of iron or steel?

No, but I would use thin pointy ones anyway so they show the
direction of the field.

Just now I filed a nail with two different sizes of file. The
bigger, slightly coarser file gave bigger filings, but it isn't
clear that the size and shape distribution is different.

One thing that *is* very different: I put twice as much time
and effort in with the smaller file, and got 1/10th the amount
of filings. I need a vise to hold the nail. I need a workbench
to hold the vise. I need a workroom to hold the bench. I need
a house to hold the workroom. I can't afford a vise.

Use the big ones ;-)

I'm answering my own questions. I made the filings onto a hard
plastic tray from the kitchen. It seems to have lower friction
than some paper. When I apply a magnet, the itty-bitty little
filings climb up on each other's shoulders to do a flea-circus
stunt where they make relatively huge needles (compared to the
size of the filings) which stand up from the tray surface.

With just a single filing, is there any evidence of
preferred locations that it wants to go to?

George