Electrical conductivity

Categories: Electrochemistry | Electrical phenomena | Physical quantity

Electrical conductivity is a measure of how well a material accommodates the transport of electric charge. Its SI derived unit is the siemens per metre, (A²s³m^-3kg^-1) (named after Werner von Siemens).

Electrical conduction is an electrical phenomenon where a material (solid or otherwise) contains movable particles with electric charge, which can carry electricity. When a difference of electrical potential is placed across a conductor, its movable charges flow, and an electric current appears. Conductivity is defined as the ratio of the current density to the electric field strength. It is the reciprocal of electrical resistivity.

Electrical conductivity may be represented by the Greek letters κ, σ or γ.

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Classification of materials by conductivity

Scientists often divide materials into three classes based upon their respective conductivities:

A conductor such as a metal has high conductivity.
An insulator like glass or a vacuum has low conductivity.
The conductivity of a semiconductor is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or certain frequencies of light.

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Some typical electrical conductivities

Silver: 63 · 10⁶ S/m (630,000,000,000 µS/cm; highest electrical conductivity of any metal)
Sea water: 5 S/m (50,000 µS/cm)
Drinking water: 0.005 – 0.05 S/m (50-500 µS/cm)
Ultra pure water: 5.5 · 10^-6 S/m (0.055 µS/cm)

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Electrical conductivity

Classification of materials by conductivity

Some typical electrical conductivities

See also