Magnet Myths and Misconceptions

[Newton II]

What about origin of magnetic field?

An idle electron produces only electric field but when it starts moving it produces magnetic field.  What makes a moving electron to produce magnetic field? Does a moving electron produce both elctric field and magnetic field or only magnetic field?

A permanent magnet creates magnetic field around it for infinite time without losing energy of its electrons. Does it mean that magnetic field is created out of nothing?  Does a moving electron dig out energy from vaccuum (ether) to create magnetic field around it?

Why should a moving electron produce magnetic field?

[Pirate88179]

Bill,

My first question would be, when the magnets separated are you quite sure both were at their original orientation of N to S? Or did one flip polarities?

I've glued two of those radio shack flexible magnets (about 1/8" thick) back to back and eventually, one had a magnetic "bubble" (a round zone of opposite polarity to the rest of the magnet) in it when I separated them later.

I have worked with magnetizing guitar pickup magnets (Alnico) and also slightly demagnetizing them by bringing a neodymium close to them. If you are not careful and get too close, the alnico magnet will suddenly flip poles and be fully magnetized in the opposite direction.

Good question.  I have no idea as I never thought to mark them n/s either before, or after my little experiment.  When I said that they had their "normal" N/S poles once they came apart, it is easily possible that one of them switched polarity.  I have tons of neos around here now, I could try it once again and, this time, keep track of the poles.  It would be interesting to see if that is what happened.

Thanks,

Bill

[TinselKoala]

Poynt99, MH.... Bravo!

Let me put in a couple of cents worth here as well.

Magnetic field lines have no real existence. They are like contour lines on a terrain topographical map, or isobars on a weather map. That is, they are mathematical fictions that we use to focus upon details of the underlying phenomenon: elevation in the case of the topo map, pressure and wind with isobars, and the _direction and strength of the field gradient_ for magnetism and electrism. (I just made that word up to denote the electric field phenomenon.)

The concept of the "field line" has a rigorous mathematical description that permits us to talk coherently about features of the underlying phenomenon. Calling that underlying phenomenon a "field" simply describes the fact that there is a region in space where test particles tend to move in certain ways. The magnetic field lines are a map of this tendency of probe particles to move and are a rigorous mathematical statement of how they move, that can be used in calculations. And since we can't explain these motions without the concept of force, we can talk about, define, calculate and use the force that is moving these test particles, using the concept of "lines of force" or "field lines".

You can even use a primitive analog indicator to approximate the results of these calculations: mix some iron filings in glycerine to make a ferrofluid, or sprinkle some on a piece of paper over a magnet. Or use the same system in a solid state: the green magnet-field-viewing film.

Just as there are no isobars, but there is a wind... just as there are no contour lines, but there are mountains... there are no field lines in reality, even though the "field" itself exists.

[MileHigh]

TK:

Yes indeed that's a great point about the myth of "field lines."  Many times I have read postings making references to "breaking field lines" where the poster was talking about literal magnetic field lines.  There is even a "paper" that is floating out there that is all written around the concept of breaking literal "field lines."

Another myth that should bite the dust!  <thump> <thump> <thump>

MileHigh

[TinselKoala]

http://www.youtube.com/watch?v=YhiAIsJCS9Y
(watch, read description and comments)

http://en.wikipedia.org/wiki/Magnetic-core_memory

http://www.mqitechnology.com/downloads/articles/MagnetizingGuide.pdf


Aaaaand.... discuss.