Electrical resistivity and conductivity
Electrical conductivity is a physical property that characterizes the ability of a substance to conduct an electric current. It plays a crucial role in determining whether a material functions as an insulator or an electrical conductor and is instrumental in substance identification.
Electric current is comprised of mobile charge carriers and is induced by a voltage difference between two poles. The material situated between these poles influences the magnitude of the electrical current flowing at a given voltage.
The ratio of current (I) to voltage (U) is known as electrical conductance (G), expressed by the equation G = I / U.
Electrical conductance is contingent on both material properties and dimensions. A larger cross-sectional area and a shorter distance between the poles result in increased current flow. To make generalized statements about a material, the dependence on dimensions is mitigated by relating conductance (G) to the cross-sectional area (A) and distance (l), yielding the electrical conductivity (sigma) of a substance:
\[ \sigma = \dfrac{G \cdot l}{A} \]
The unit of electrical conductivity is Siemens per meter [S/m].
The term “electrical resistance” is the reciprocal of conductance, and specific electrical resistance is the reciprocal of conductivity.
Conductivity measurement is typically conducted indirectly, measuring the current under defined conditions at a given voltage. Modern instruments provide direct values by converting the determined current using device constants.
It’s essential to note that electrical conductivity is temperature-dependent. The correlation between electrical quantities and temperature is further explored in the field of thermoelectrics.
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