Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current. The conductivity σ is defined as the ratio of the current density to the electric field strength :
Conductivity is the reciprocal (inverse) of electrical resistivity and has the SI units of siemens per metre (S·m-1) i.e. if the electrical conductance between opposite faces of a 1-metre cube of material is 1 Siemens then the material's electrical conductivity is 1 Siemens per metre. Electrical conductivity is commonly represented by the Greek letter σ, but κ or γ are also occasionally used.
An EC meter is normally used to measure conductivity in a solution.
The degree of doping in solid state semiconductors makes a large difference in conductivity. More doping leads to higher conductivity. The conductivity of a solution of water is highly dependent on its concentration of dissolved salts and sometimes other chemical species which tend to ionize in the solution. Electrical conductivity of water samples is used as an indicator of how salt-free or impurity-free the sample is; the purer the water, the lower the conductivity or higher.
|Electrical Conductivity (S·m-1)||Temperature(°C)||Notes|
|Silver||63.01 × 106||20||Highest electrical conductivity of any known metal|
|Copper||59.6 × 106||20|
|Annealed Copper||58.0 × 106||20||Referred to as 100% IACS or International Annealed Copper Standard. The unit for expressing the conductivity of nonmagnetic materials by testing using the eddy-current method. Generally used for temper and alloy verification of Aluminium.|
|Gold||45.2 × 106||20||Gold is commonly used in electrical contacts|
|Aluminium||37.8 × 106||20|
|Seawater||5||23||Refer to http://www.kayelaby.npl.co.uk/general_physics/2_7/2_7_9.html for more detail as there are many variations and significant variables for seawater. 5(S·m-1) would be for an average salinity of 35 g/kg at about 23(°C) Copyright on the linked material can be found here http://www.kayelaby.npl.co.uk/copyright/|
|Drinking water||0.0005 to 0.05||This value range is typical of high quality drinking water and not an indicator of water quality|
|deionized water||5.5 × 10-6||changes to 1.2 × 10-4 in water with no gas present|
An alternative description of the response to alternating currents uses a real (but frequency-dependent) conductivity, along with a real permittivity. The larger the conductivity is, the more quickly the alternating-current signal is absorbed by the material (i.e., the more opaque the material is). For details, see Mathematical descriptions of opacity.
The temperature compensation slope for most naturally occurring waters is about 2 %/°C, however it can range between (1 to 3) %/°C. This slope is influenced by the geochemistry, and can be easily determined in a laboratory.
At extremely low temperatures (not far from absolute 0 K), a few materials have been found to exhibit very high electrical conductivity in a phenomenon called superconductivity.
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