Magnetic dipole magnetic dipole as the distance from the source increases. In classical physics, the magnetic field of a dipole is calculated as the limit of either a current loop or a pair of charges as the source shrinks to a point while keeping the magnetic moment constant. For the current loop, this limit is most easily derived for the vector potential. Outside of the source region, this potential is (in SI units) with 4"π r" being the surface of a sphere of radius "r"; and the magnetic flux density (strength of the B-field) in teslas is In spherical coordinates with the
Mass flux Mass flux In physics and engineering, mass flux is the rate of mass flow per unit area, perfectly overlapping with the momentum density, the momentum per unit volume. The common symbols are "j", "J", "q", "Q", "φ", or "Φ" (Greek lower or capital Phi), sometimes with subscript "m" to indicate mass is the flowing quantity. Its SI units are kg s m. Mass flux can also refer to an alternate form of flux in Fick's law that includes the molecular mass, or in Darcy's law that includes the mass density. Unfortunately, sometimes the defining equation for mass flux in this