Series for Computing Current Flow in a Rectangular Block

A new method of measuring the electrical resistivity of anisotropic materials has been proposed by Montgomery. His method depends on the value of a quantity M associated with the current flow in a rectangular block of material. The current enters and leaves the block at two adjacent corners of a given face. M is proportional to the voltage between the two remaining corners of the face and depends only upon the dimensions of the block. Here methods for computing M are developed. Several series are given, values of M tabulated, and various asymptotic expressions are derived.