Symbol Definition Units
Ae Effective Cross-Sectional Area - In a structure containing a non-uniform cross section, the effective magnetic cross section is the area of a structure with uniform cross section which is equivalent to the first for purposes of magnetic calculations. Also called Ac. mm2
AL Inductance Factor - Industry standard method of expressing the inductance of a magnetic core, independent of turns. The inductance (in µH) of a coil with N turns wound on a core with known AL is N2•AL/1000. AL is established at low flux density (<1mT) and at a low enough frequency to avoid error from resonance or frequency response.  mH/1000T
awg American Wire Gauge - also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system  
B Magnetic Flux Density - The number of lines of magnetic force per square centimeter of material. Also called Induction or Magnetic Induction. Gauss
BH Curve BH Curve -  Relation between magnetic induction B and magnetizing force H for a magnetic material.  Also called Magnetization Curve or Hysteresis Loop.  
Br Remanence - The residual flux level in a core at H = 0. The measured Br depends on the recent magnetization history of the core. Br/Bmax is thesquareness. Gauss
Bmax Saturation Flux Density - The maximum flux density a magnetic material can accommodate.  At Bmax, further increases in H result in no significant increase in B Gauss
H Field Strength - The externally applied magnetic field.  Also called Magnetizing Force or mmf(Magnetomotive Force.) Oersted
HC Coercive Force - The reverse magnetic field needed to reduce a previously magnetically saturated core from B=Br to B=0. Hc is a measure of the width of the hysteresis loop at low frequency. Oersted
L Inductance - The magnetic flux linkage in Maxwell-turns per ampere of magnetizing current. Henries
le Magnetic Path Length - The effective length along which field strength is applied for a particular core shape and dimension.  
TC Curie Temperature - Temperature at which a ferromagnetic material loses its ferromagnetism and becomes paramagnetic (μe approaches 1).  For ferrites, the effects of exceeding Curie temperature are fully reversible. ºC

Permeability - The ratio of magnetic flux density in gauss to magnetic field strength inoersteds.
μ= β/H

μe Effective Permeability - If a magnetic circuit is not homogeneous (i.e., contains an air gap), the effective permeability is the permeability of a hypothetical homogeneous (ungapped) structure of the same shape and dimensions that would give an inductance equal to the gapped structure.  
Ve Effective Magnetic Volume - Product of Ae and le. mm3
WaAc Area Product - Product of winding window area and Ae. Also called Ap. Area product is a useful parameter for estimating the power handling capability of a core, if the frequency and circuit topology are known. cm4