Internal Impedance of Composite Conductors with Arbitrary Cross Section

A new way to calculate the internal inductance and resistance per unit length for an inhomogeneous conductor with arbitrary cross-sectional geometry is presented, based on the surface admittance boundary operator. The method is formulated in such a way, that the physical meaning of the internal impedance is clarified, as obtained by disregarding the external magnetic field. A comparison is made with the definitions known in literature to determine the internal impedance. In a number of numerical examples, the differences between those definitions are elucidated, and some physical properties of the internal impedance are investigated.