Magnetic dipole
A magnetic dipole is the simplest form observed, occurs in the magnetism. All complicated magnetic structures can be composed of dipoles.
Absence of magnetic charges
Magnetic field lines have no ends. The magnetic field is always free of sources, ie divergence-free.
About magnetic monopoles (analogous to individual positive or negative electric charges ) is speculation, but it could be detected so far none. [Note 1] Although can be individually addressed as a magnetic north or south pole in commercial bar or horseshoe magnet as well as in long solenoids both ends. When trying to separate them, but occurs at the interface, a new pair of such poles, so that one obtains two dipoles.
Occurrence and significance of magnetic dipoles
According to classical electrodynamics, a magnetic dipole is generated by a circular current which flows around an area. Its magnetic dipole moment is:
In addition, all elementary particles, provided they are electrically charged and an intrinsic angular momentum (spin ), also magnetic dipoles with a different depending on the particle dipole moment. These include quarks and electrons and therefore also the constructed therefrom atomic nuclei and atoms. These dipoles are important in atomic, nuclear and elementary particle physics. The observation of space quantization, after an elementary dipole moment can take to an external magnetic field only certain angle, has contributed significantly to the elucidation of the structure of particles and atoms. See also: magnetic moment of particles and nuclei, Stern-Gerlach experiment, normal and anomalous Zeeman effect, nuclear and electron spin resonance.
Field of the dipole
A magnetic dipole generates a magnetic field at a given location at a greater distance due to the magnetic flux density
Is the amount of, is the magnetic field constant and is the spherical surface at a distance.
This formula is valid regardless of the shape and size of the current loop, the magnetic coil, the bar magnet or the atom, if large is against their spatial extent.
In an external magnetic field applied to a magnetic dipole, the torque
And he has a dependent of the angle to the field direction potential energy
If the field is inhomogeneous, the force acts in the first order
With the nabla operator.
The magnetic properties of a piece of matter are determined by the magnetic dipoles which are already present in it are of constant size ( as in ferro -, antiferro - and paramagnetism ) generated or only when you turn the field ( diamagnetism ).