| for a magnetic core operating within the Rayleigh region, and having given geometry and material properties, the magnetic path length, the cross-sectional area and the volume that a hypothetical toroidal core of the same material properties and of radially thin uniform cross-section should possess to be magnetically equivalent to the given core|
Note 1 – The effective dimensions are as follows:
effective cross-sectional area
effective magnetic path length,
where C1 and C2 are the appropriate core factors hence:
Note 2 – These formulae can also apply to a magnetic circuit operating outside the limit of the Rayleigh region provided the magnetization can be assumed to be uniform, for example as in an Epstein square.