Conductivity

Definition

A measure of a material’s ability to transmit a flow across it under given conditions; the flow can be of heat, electricity, magnetism, light, sound and, of especial interest to engineering geology, fluids (water, gas, and oils).

To obtain a measure of conductivity, a defined volume of the material is used, e.g., a disc or column; a volume of shape that has radial symmetry. Imagine a column for the purposes of this measurement; it has three boundaries: one at the top through which the flow of whatever is being measured enters the material, one at the bottom through which whatever is flowing leaves the material, and the sides of the column are its third boundary and for the purposes of this measurement they are controlled so that no flow can cross them; they can be sheathed in some way. The distance between the upper and lower boundaries is (L) in units of length, and the area of each of the upper and lower boundaries is (A) in units of area (British Standard Normative tests...