Iron & Magnetic Fields: Permeability or Screening?

[Dyon]

Maybe a picture will help.

First thing to straighten out is magnetic flux , like current, makes its way back to the source. Think "Closed Loops".So in OP's first picture
here's what i would add to hopefully resolve the misunderstanding.

View attachment 101112

Flux (in red) will prefer the permeable iron slab , not the impermeable air behind it. (well, permeability of just 0.00000126)

That image in MarcusL's post 14 is just great , shows how an iron pipe routes flux around its hollow middle. That's why we use iron conduit for some sensitive signal wires in the power plant.

Thanks for taking the time to draw the magnetic lines in red. But I go back to my initial point and say you don't have any experimental proof that the lines actually go so deep in the iron plate, I think they enter the plate (if at all) very superficially, most of the lines just glide past the surface (iron screens them), that's why the poles seen at the edges are towards the magnet side and not also to the rear side. Also I have a great deal of trouble understanding why a N pole is not induced at A on the plate since iron is such a "high permeability" material, which also tells me iron's screening is real and not due to "high permeability".

The iron pipe routing the flux around its hollow middle can be seen also as a proof that iron is not permeable to magnetism, thus prevents the magnetic field from passing through. If the pipe were made of plastic, that would be a "highly permeable" material to the magnetic field since it let's the magnetic field pass through.

 

[Dyon]

Any demonstration of this sort would not be very definitive. I think if you have any kind of resources available to work with magnetic materials of various kinds, you could do a lot of interesting things including experiments to create permanent magnets (even spherical ones), and even see what kind of field is necessary to reverse the magnetization. I do suggest if you have further interest in the subject, you google about experiments that have already been performed.

Thanks.
In order to avoid the magnetic field lines' tendency to return to the other pole, I think I will work with a very long magnet to have the magnetic lines leaving the pole radially.

 

[Dale]

I will probably write an article arguing against this common belief.

I think it is time to close this thread.