MAGNETIC CONDUCTIVITY

MAGNETIC
CONDUCTIVITY

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The general scientific idea that ferromagnetic materials become temporary magnets when subjected to magnetic field can't possibly stand to scrutiny. As a blatant example, any ferromagnetic material is constantly immersed in the magnetic field of earth yet, unless permanently magnetized, it does not exert magnetic force on any other ferromagnetic material in its proximity. In simple terms, any two chunks of soft iron do not stick together just because they are both immersed in the earth magnetic field. Neither of them show properties of a permanent magnet. Therefore, the term temporary magnet is scientific gibberish irrelevant to reality.

The only person who came to somewhat better understanding of magnetic field as far as I know was Edward Leedskalnin with his magnetic current, even though he has mixed up magnetic and electric into one. What is obvious though is, that ferromagnetic materials are the best conductors of magnetic field.

When we line up two permanent magnets with unlike poles toward each other, with a gap between them, the magnetic field "lines" create pattern between the poles described by root to stalk onion section. When we place a piece of ferromagnetic material between the magnetic poles, the single onion shape field lines become concentrated through the ferromagnetic material creating two onion like patterns. This experiment itself can be interpreted two ways. The first interpretation is that the ferromagnetic material became a temporary magnet. The second one is that the ferromagnetic material only concentrates the magnetic lines of force, because it is much better able to conduct magnetic field than the air.

When we place a permanent speaker magnet on a large sheet of steel, or iron if you wish, the magnetic lines of force exit the exposed side of the magnet and enter the sheet on the near side of the speaker magnet. Yet no magnetic lines of force can be observed exiting the steel sheet on the far side of the magnet. Contrary to this observation, when the same speaker magnet is placed on a sheet shaped magnet as it attracts, the magnetic lines of force go all the way around the magnets joining their far sides (poles). The only interpretation of this result is that the ferromagnetic sheet leads the magnetic field through itself and it contradicts the notion that the ferromagnetic material becomes a temporary magnet.

It is truth that the internal structure of the ferromagnetic material temporarily changes while immersed in a magnetic field, but this fact alone does not constitute a good reason to call it a temporary magnet. The sheet has not become a dipole.

The actual attraction of two magnets is caused among other reasons by distortion of the magnetic field. An ideal magnetic field, if possible, would describe a series of concentric lines. This never happens in the real world with the exception of the field around a wire under DC (Direct electrical Current). All other options include a magnetic body, in which the mean magnetic intercrystalline structure is elongated in the North-South direction, like in a typical bar magnet.

Taking another example, we can readily observe that a ferromagnetic core of a classic transformer does not show any outside magnetic properties as long as it is designed with sufficient core mass and the core mass does not become saturated. In other words, well designed transformer core is capable to completely contain the magnetic field of its coils, leaving no magnetic lines extending anywhere outside the core. This again shows quite clearly that the transformer core material only leads the magnetic field.

A DC electromagnet, where the coil has a central ferromagnetic core, joined by a ferromagnetic cap to a ferromagnetic shell enveloping the coil an all sides except the side opposite to the cap, shows again that the ferromagnetic material only leads the magnetic field to the open face of the core and the open face of the shell. When the electromagnet is not engaged on a ferromagnetic substrate, its field lines describe again the semicircular onion like pattern between the core face and the shell face. When the electromagnet is placed on a ferromagnetic substrate, the magnetic lines of force become completely contained in a more or less circular path through out the ferromagnetic materials of the core, the cap, the shell and the ferromagnetic substrate as long as the substrate does not reach its magnetic saturation.

The force between any two magnets is not caused by some mysterious enigma, but by the two inherent properties of magnetic field.

The first property of a magnetic field is that it always attempts to not exist. This may sound funny till we begin to understand that the magnetic field is an external balancing act of internal electric currents. Whether these currents are inter-atomic, inter-molecular and intercrystalline within a permanent magnet, or exist as standard electric currents in conductors makes only geometric difference of the field structures. It does not make difference to the qualitative aspect of magnetism properties. In other words, if we should represent magnetic filed as a set of lines, each line tends to shrink into nonexistence.

This means that the magnetic field is under constant constrain, which is exactly the reason why the lines of force assume the linear (straight) shape close to the central axis between unlike magnetic poles and why they assume a semicircular shape around a single bar magnet as well as between the far faces of two bar magnets with unlike poles toward each other.

The resulting attractive force is a result of a few aspects of the magnetic field. The bellow considers only the simplest configurations to allow you understand the basic relationships, which can of course be brought to great complexity.

Attractive Arrangement

1) Function of distance between two bar magnets: The larger is the distance between magnetic poles, the more lines of force and therefore magnetic field of each magnet closes around each magnet itself disengaging from the attractive relationship of a shared (common to both) two bar magnet field.

2) Function of bar magnet length. The longer are the bar magnets, the les pronounced is the function #1 and the closer is the attractive force math relationship to square of distance.

3a) Function of shape. The greater are the pole areas of the bar magnets, the closer is the attractive relationship force between the poles to the cube of distance rather than the square of distance.

3b) The flatter (as opposed to lets say hemispherical shape of the magnet poles) are the magnetic poles, the closer is the attractive force strength function to the cube of distance.

"Repulsive" Arrangement

1) Function of distance between two bar magnets. The larger is the distance between two alike poles, the les distortion of the curvature of the two individual (not shared) magnetic fields, the lesser the repulsive force.

2) Function of shape. The larger is the area of the pole faces, the closer is the function of repulsive force to cube of distance.

2b) The flatter (as opposed to lets say hemispherical) are the magnetic poles, the closer is the function of field strength to cube of distance.

The above can be of course combined as per mutual angles etc. The most important part of this write up is the understanding that:

a) Magnetic field becomes more and more shared as specified with shortening distance between;

• a magnet and a ferromagnetic material
• two unlike (attractive) oriented permanent magnets
• conductor under AC (Alternating Current) and a ferromagnetic material (albeit alternating in orientation)
• Conductor under AC and a permanent magnet (resulting in alternate reorientation of at least one of them if permitted by external mechanical constraints.
• Conductor under DC (Direct Current) and a ferromagnetic material
• Conductor under DC and a permanent magnet if permitted to orient itself by external mechanical constraints.

b) Magnetic field is not shared between repulsive orientation sources (magnets) when retained in an ideal alike orientation, but become more and more shared as the orientation is being allowed to naturally align to unlike (attractive) orientation.

The above are the reasons for the difficulties in assigning a simple particular mathematical formula to the strength of magnetic field interaction.