Plotting magnetic field lines between two adjacent NS poles

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Discussion Overview

The discussion revolves around the behavior of magnetic field lines between two adjacent disc magnets with alternating poles. Participants explore the characteristics of the magnetic field lines, particularly the transition point where the field lines change direction from one magnet to the other, and the complexities involved in simulating this system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the arrangement of two axially magnetized disc magnets and the observed behavior of magnetic field lines when iron filings are sprinkled on them.
  • Another participant suggests that the point where field lines change direction may not have a specific name but can potentially be simulated, noting the challenges of accurately simulating finite-sized magnets.
  • A further inquiry is made about the difficulties in simulation, particularly regarding nonlinearities in shape and the influence of magnetization on the field geometry.
  • One participant explains that the complexity arises from the interdependence of magnetization and the fields produced by other parts of the magnets, complicating evaluations.
  • Another participant questions whether there are significant differences in properties and effects on nearby particles between the field lines connecting adjacent magnets and those connecting the same magnet.
  • A response clarifies that while numerical simulations can handle the size of the setup, accurately simulating the solid material poses challenges, and emphasizes that field lines are not physical entities.

Areas of Agreement / Disagreement

Participants express varying views on the naming of the transition point and the feasibility of simulation, with some agreeing on the complexity of the task while others raise different aspects of the problem. No consensus is reached regarding the properties of the field lines or their effects on nearby particles.

Contextual Notes

Participants acknowledge the challenges of simulating finite-sized magnets and the influence of magnetization on field geometry, but do not resolve these complexities or provide definitive solutions.

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This question is regarding the magnetic field lines around two abutting alternating poles.
Take two axially magnetised disc magnets and place them next to each other (like tangent circles), so on each side the adjacent or neighboring magnet is of the opposite pole.

By sprinkling iron filings on the surface of these two abutting alternating pole magnets you can see the magnetic field lines closing out by leaving the north pole of one magnet and entering the south pole of the adjacent magnet. That is until you get far enough away from the adjacent magnet, that the field lines now leave the north pole of the magnet, go in the opposite direction and enter the south pole of the same magnet. That is instead of field lines being directed to the opposite pole of the adjacent magnetic body, they are directed to the opposite pole of the same magnetic body (underneath).

Does the point at which the field lines change from being directed to the adjacent magnetic body to the same magnetic body have a name and is it possible to calculate where this point exists assuming both magnets are identical in size and material?

(I hope my description is adequate, let me know if I should add a photo). Thank you.
 
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I don't think it has a special name. It is possible to simulate the system to find this point, but magnets with a finite size are very tricky to simulate accurately.
 
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mfb said:
I don't think it has a special name. It is possible to simulate the system to find this point, but magnets with a finite size are very tricky to simulate accurately.

Very interesting. Do nonlinearities in the shape make it hard to do the integrations?
Or what is the source of the difficulty?
 
The field geometry is based on the magnetization of the ferromagnetic material, but this magnetization also depends on the fields of other parts of the magnets - which then influences the field again and so on. The first part is easy, the second effect is hard to evaluate.
 
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Thank you mfb.
I guess having vectors come from so many points makes it complex?

If comparing the two fields, i.e. the field lines joining the adjacent magnetic body and the field lines joining the same magnetic body.
Is there a significant difference in their properties and their effects on other particles in their vicinity? Thank you.
 
The size of the setup is no problem - a computer can easily handle that with a numerical simulation. Getting the simulation of the solid material right is the challenging part.

Field lines are not physical objects. The field strength and direction depends on the location, but apart from that there is no difference.
 

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