Magnetic permeability is the measure of magnetization that a material (e.g. actuator/slug in a solenoid) obtains in response to an applied magnetic field. Therefore the more conducive a material is to a magnetic field, the higher its permeability. Magnetic permeability is typically represented by the Greek letter μ. The term was coined in September, 1885 by Oliver Heaviside. The reciprocal of magnetic permeability is magnetic reluctance.
In SI units, permeability is measured in the henries per meter (H/m), or newtons per ampere squared (N/A[SUP]2[/SUP]). The permeability constant (μ[SUB]0[/SUB]), also known as the magnetic constant or the permeability of free space, is a measure of the amount of resistance encountered when forming a magnetic field in a classical vacuum. The magnetic constant has the exact value µ[SUB]0[/SUB] = 4π×10[SUP]−7[/SUP] approximately 1.2566370614…×10[SUP]−6[/SUP] H/m or N/A[SUP]2 [/SUP]
“Magnetic B field” is the magnetic field density represented by the symbol B and measured in Tesla (T) in SI units.
Inductance is the AC parameter in a purely inductive circuit that limits the magnitude of the current flowing in that circuit and is represented by the symbol L and is measured in henries (H). In a purely inductive circuit, when the supply voltage begins to increase, the current cannot increase in sympathy with it because a back e.m.f. is induced in the winding of the inductance (coil), and this e.m.f. opposes the change of current. The net effect is that the rise of current lags behind the rise of voltage. Since the magnitude of the back e.m.f. is related to the rate of change of current and must be equal in value to the supply voltage, then the magnitude of the current is also limited by this phenomenon.
