Note on the Definition and Calculation of the Per-Unit-Length Internal Impedance of a Uniform Conducting Wire

The Thevenin theorem is used to define the internal impedance per unit length (p.u.l.) of a uniform conducting wire of arbitrary cross-sectional geometry. Two different boundary value problems are then proposed for the calculation of the internal impedance of the wire, which are both consistent with the proposed Thevenin theorem-based definition. For the important case of rectangular conducting strips, an advantage is taken of the separable cross-sectional geometry for the development of analytical expressions for the internal impedance of the wires. It is shown that these expressions reproduce correctly both the resistance of the wire p.u.l. length at dc and the trend of R(omega) ap omegaL(omega) at sufficiently high frequencies such that the skin effect is well developed.