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In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N/A 2). The permeability constant μ 0, also known as the magnetic constant or the permeability of free space, is the proportionality between magnetic induction and magnetizing force when forming a magnetic field in a classical vacuum.
A dominant nonlinear response, however, can be derived from the hysteresis-type dependence of the material's magnetic permeability on the magnetic component of the incident electromagnetic wave (light) propagating through the material.
Nonlinear dynamics can occur when electromagnetic fields couple to matter that follows nonlinear dynamical laws. [29] This is studied, for example, in the subject of magnetohydrodynamics, which combines Maxwell theory with the Navier–Stokes equations. [30] Another branch of electromagnetism dealing with nonlinearity is nonlinear optics.
Highly magnetic materials have a reduced skin depth owing to their large permeability as was pointed out above for the case of iron, despite its poorer conductivity. A practical consequence is seen by users of induction cookers , where some types of stainless steel cookware are unusable because they are not ferromagnetic.
The relation between the magnetizing field H and the magnetic field B can also be expressed as the magnetic permeability: = / or the relative permeability = /, where is the vacuum permeability. The permeability of ferromagnetic materials is not constant, but depends on H .
In this experiment, a static magnetic field runs through a long magnetic wire (e.g., an iron wire magnetized longitudinally). Outside of this wire the magnetic induction is zero, in contrast to the vector potential, which essentially depends on the magnetic flux through the cross-section of the wire and does not vanish outside.
Effective permittivity and permeability are averaged dielectric and magnetic characteristics of a microinhomogeneous medium. They both were derived in quasi-static approximation when the electric field inside a mixture particle may be considered as homogeneous. So, these formulae can not describe the particle size effect.
In electromagnetism, permeance is the inverse of reluctance.In a magnetic circuit, permeance is a measure of the quantity of magnetic flux for a number of current-turns. A magnetic circuit almost acts as though the flux is conducted, therefore permeance is larger for large cross-sections of a material and smaller for smaller cross section lengths.