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Interesting, but pretty irrelevant


old man emu
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When people try to explain some natural phenomenon, they use diagrams to help illuminate the idea. For example, when we discuss airflow and Lift we use a diagram like this:

 

image.png.9ba22413d0d2f1dca7765b5522533b4d.png

We all accept that each of those lines represent the path of a single cubic volume of air, and that we know that there are similar cubes in the spaces between lines. We just don't show them in order to make the diagram clear.

 

When we talk about magnetic field lines, we draw the diagram in a similar way, and assume that there are an infinite number of lines of magnetic force between the two poles.

image.jpeg.9935f93c58f0760ffc22a722268af77f.jpeg

How its it, however, that if you put piece of paper over a bar magnet, and sprinkle iron filings on the paper, you get the filings making these lines?

 

Image result for magnetic field lines

 

Why are there spaces between the lines? Are there no magnetic forces at work in those gaps?

 

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I think it is because each iron particle become polarized. The filings want  to stick together end to end and not laterally.  It is a great question and I admit I did not know the answer. 

 

 

"The actual magnetic field itself does not have "lines" in it; the "lines" are solely the iron filings becoming polarized themselves, reacting to each other and the field, lining up N and S with respect to each other in the field. If you could see the actual fields of force, it would be shaded and gradient, with a heavier, thicker shade near the stronger part of the magnet, fading the further you get from the source. And in all 3 dimensions, which iron filing demonstrations cannot reproduce. Ferrofluids will react in all 3 dimensions and can more accurately reproduce a field, except for gravity creating a weight restriction. Holding a strong magnet in front of a CRT-type monitor with a white screen can also give a representation of the fields, without any "lines of force" visible. The issue with using ferro/magnetic materials to view a field is, the materials themselves become magnetized and change the original field to include their own influence."

References

  1.  Visualization of fields and the divergence and curl. Notes from a course at the Massachusetts Institute of Technology. [1]
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Thank you Octave, I'd never thought deeply enough about magnets to ask the question. But the answer does make logical sense.

 

Now, tell me what makes static magnetism (physically immobile) work and why does it only work on certain mmaterials?

 

IE,

What physics caused it attract, or to repel?

 

Edited by nomadpete
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2 hours ago, octave said:

If you could see the actual fields of force, it would be shaded and gradient,

Using iron filings introduces another factor - the alignment of atoms within the filings themselves to the lines of magnetic force of the bar magnet, making each filing a bar magnet which will align itself with the opposite "pole" of the next filing.

 

post-74263-0-43192400-1426531588_thumb.jpg

 

The lines of filings we see when we use filings are the equilibrium positions of each filing within the magnetic field. A magnetic field is a vector field that describes the magnetic influence on magnetic materials. 

 

The magnetic flux density or just magnetic field is a vector field. The magnetic field vector at a given point in space is specified by two properties:

1.  Its direction, which is along the orientation of a compass needle.

2.  Its magnitude (also called strength), which is proportional to how strongly the compass needle orients along that direction.

 

So, the voids between the lines are the places where the sum of the vectors is zero, or very close to zero. Maybe the mass of the filings is something that produces very distinct lines. I wonder what the lines would look like if you used very fine iron dust.

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5 hours ago, old man emu said:

How its it, however, that if you put piece of paper over a bar magnet, and sprinkle iron filings on the paper, you get the filings making these lines?

 

Image result for magnetic field lines

 

Why are there spaces between the lines? Are there no magnetic forces at work in those gaps?

I get the same sort of headache from jet engine intake diagrams; oblique shock, normal shock etc.. that's what your pic reminds me of.

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You guys are touching on modern physics. This all started with the ex-bookbinder  Faraday measuring electrical and magnetic things. Then a shy Scottish lord ( Maxwell) distilled this work into some equations. Then a patent examiner called Einstein, struck by the "beauty" of these equations formulated Relativity from them.

For myself, I find differential vector equations way  too hard.     I wonder if a brain transplant would help.

Once I tried to explain to myself the derivation of e=mcsquared.  Same result.

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The filings are part of the picture and affect the way it's perceived. It's a force field not connected lines.(The orbit of an electron about the atom's nucleus is similar). Magnets attract and repel, drift and form clusters if you use particles which react to each other and the magnetic field they are in.. Gauss (CGS) has become Tesla as a measurement of strength. Nev

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On 09/02/2021 at 10:00 PM, old man emu said:

I wonder what the lines would look like if you used very fine iron dust.

 

On 09/02/2021 at 10:02 PM, octave said:

That is your tomorrow sorted OME,     we will await you video

 

I'm drawn to that task like centripetal force draws in a circulating mass. It's only my rotational inertia that prevents the fuge of my task from the centri-.

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