NOTE 1 – For insulating materials the volume resistivity is usually determined by means of measuring electrodes arranged on a sheet of the material.

NOTE 2 – According to IEC 60050-121: Electromagnetism,“conductivity” is defined as “scalar or tensor quantity the product of which by the electric field strength in a medium is equal to the electric current density” and “resistivity” as “the inverse of the conductivity when this inverse exists”. Measured in this way, the volume resistivity is an average of the resistivity over possible heterogeneities in the volume incorporated in the measurement; it includes the effect of possible polarization phenomena at the electrodes.