Iron filings and bar magnets
When you look at the pattern of iron filings on a glass or plastic over a short bar magnet you see lines of magnetized iron filings stuck together by magnetism. The iron filings have become lines of tiny series magnets, lines of tiny series dipoles, curving around to the opposite poles of the bar magnet. Energy is stored in each dipole. We have serial tensile forces. We have to add the binding energy of the dipoles to pull them apart. The lines of tiny series magnets repel each other which accounts for their spacing. The lines repel each other because their poles point in the same direction and like poles repel. The lines may stick together and clump when they are close to each other and their centers are offset. K&J has an interesting magnetic field calculator which shows a pattern similar to the above for thin disk magnets. Helmholtz coils are similar. See hyperphysics for a loop or ring current.
We might say that magnetic field lines originate at the top of a magnet and return at the bottom of a magnet as they do in the figure above. A much longer magnet would have its field lines stretched into a solenoid, loosing its circular symmetry, but the lines still leave the top and return to the bottom of the magnet. When this long magnet is bent and closed into a loop, its top and bottom and the source and destination of the lines merge so the lines disappear so the magnetic field in a ring is concealed. If the green magnet above is stretched into a long bar magnet and bent and closed into a loop then the external field of the magnet disappears. The huge ring currents in the electron and proton if seen would have huge magnetic fields which would disrupt the orbits of the electron and proton in the atom but since the ring current is closed into a loop the external fields disappears. The ring currents still cause the magnetic moment so we are left with the peculiar situation of a magnetic moment without an obvious source magnetic field. In the electron and proton where the charge q moves at the speed of light c we have,
q*E = q*c*B, which can be written
E = c*B,
E2 = c2*B2,
E2 = B2/(e0*u0),
E2*e0 = B2/u0, energy/volume Coulomb repulsion pressure = force/area magnetic pinch pressure. Is this something which suppresses the huge magnetic field of the electron which is due to its magnetic moment?
Rings of magnetic beads or spherical magnets have a lot of tensile strength and are hard to pull apart. They are series magnetic dipoles. Rings hide the bipolar glue of their dipolar units which holds them together in rings. Their hidden flux is confined to the ring. See helical electromagnetic waves. Toroidal transformers are used in radio work because of their low noise or signal leakage. Rings of very strong spherical magnets have a very strong internal magnetic field and a very weak external magnetic field but they still maintain their strong tensile forces. See the Beaty video. Magnets have other interesting structural assembly properties. Interesting sources are K&J and neocube. Warning! Magnets can be addictive. One might be subject to spousal abuse for spending too much money on too many magnets.
In a similar way, the field lines from a charge dipole or polarized atom might leave from one end and return to the other end of the dipole so we might expect a series of charge dipoles to act like the series of magnetic dipoles and hide the majority of their lines in a ring with only minor leakage and still maintain their strong tensile forces.
Bipolar atoms stick together like magnetized iron filings or strings of magnetic beads. This is like the magnetic beads in the figure below. The ends of the rows of polarized atoms have a strong polarity and strong attractive and repulsive forces.
are a fun way to experiment with bipolar ideas. The ends of rows of magnetic beads have a strong polarity. These rows of magnets stick together because they are offset, close together and their poles point in the same direction.
Like poles repell
These rows of magnets repell each other because like charges repell.
Opposite poles attract
These rows of magnets stick together because opposite poles attract.
Loops of magnets
Magnets stick together to make a helix out of a long string of magnets. Only the ends are exposed and show the polarity. The two loops of magnets on the right attract each other because opposite poles attract. Loops of electrostatic dipoles attract each other in just this way.
Magnets and dipoles
Both have poles. Poles have polarity. Oppositely charged poles are bipoles or dipoles.
The forces between their charged ends may be expressed, by us, with parallel and perpendicular components. They assemble in complex structures.
Magnets are accessible. Magnets are magnetic dipoles which are a model for charge dipoles which are a model for gravity.