Fundamental Relationships

Read Suggestions for the Use of SI Units in Magnetism
Fundamental Units (From Resnick and Halliday, Physics, Part I, 1968, Wiley)

Coulomb's Law

Definition of magnetic permeability

Magnetic Potential

Magnetic Dipole

Intensity of magnetization

Magnetic dipole moment is an extensive quantity (like mass). In analogy with gravity, magnetic dipole moment per unit volume is  an intensive quantity (like density). This is also called the intensity of magnetization, or

I = M/volume = ml/volume = m/area

where I and M are vector quantities.

Potential due to a Dipole

The potential due to a dipole is found by summing the potentials of the individual poles:

Field of Magnetic Dipole

Fig. 4.8. Magnetic field of a dipole. Dipole m is oriented toward top of page. Vectors indicate the direction of B that would be observed at the center of each vector. Dashed contours indicate constant values of |B|, the value decreasing by a factor of 10 at each succeeding contour from the dipole; that is, if the closest contour to the dipole has the value |B| = 1, succeeding contours have the values 0.1, 0.01, and 0.001, respectively.