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-Eddy Current Inspection Formula - Electrical Resistivity and Conductivity


s = Electrical Conductivity
(MS/m or mS/cm)
r = Electrical Resistivity
(ohm-meter or mohms-cm)

Resistivity (r) is an intrinsic property of a material relating to the materials resistance to the flow of electrical current. A high resistivity indicates that a material is not a good conductor of electricity.  Resistivity is determined by measuring the electrical resistance over some length of material with a constant cross-section.  The materials resistivity is the product of the resistance value and the cross-sectional area divided by the length as given in the following equation.


ρ = resistivity (ohm meters)
R = electrical resistance of a uniform specimen of the material (ohms)
l = length of the specimen (measured in meters)
A = cross-sectional area of the specimen (meters 2)
Conductivity is calculated by simply taking the inverse of resistivity.  A material with a resistivity of 1/58 ohm-meter will have a conductivity of 58 MegaSiemens per meter.