Conductivity

The term electrical conductor is used for all materials which have charge carriers (such as valence electrons in metals), which can conduct the electrical current.

Electrical conductivity σ (sigma) is a material-specific parameter. It describes how well a material can conduct an electrical current.

The inverse of specific conductivity is specific resistivity ρ (rho). It expresses the amount of resistance a material exerts against the flow of charge carriers.

To determine these material parameters the probe geometry (length and cross-sectional area) and electrical quantities (voltage drop and electrical current or resistance) are linked together:

σ  – specific conductivity in S / m (Siemens / m, 1 m / Ω mm² = 1 MS / m)

ρ  – specific resistivity in Ω mm² / m

U – voltage drop in V (Volt)

I   – electrical current in A (Ampere)

R  – Ohmic resistance in Ω (Ohm)

l   – length of the conductor in m

A  – cross-sectional area of the conductor in mm²

In Anglo-American regions electrical conductivity is indicated using the IACS system. The specific conductivity, and thus also the specific resistivity, are temperature-dependent. In the case of metals specific conductivity generally drops with rising temperature, because the increasing thermal movement of the atoms generates more resistance to the flow of the charge carriers.