# Electrical conductivity

**Electrical conductivity**or**specific conductivity**is a measure of a material's ability to conduct anelectric current . When anelectrical 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 thecurrent density $mathbf\{J\}$ to theelectric field strength $mathbf\{E\}$::$mathbf\{J\}\; =\; sigma\; mathbf\{E\}$

It is also possible to have materials in which the conductivity is

anisotropic , in which case σ is a 3×3 matrix (or more technically a rank-2tensor ) which is generally symmetric.Conductivity is the reciprocal (inverse) of electrical

resistivity and has the SI units of siemens permetre (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.**Classification of materials by conductivity*** A conductor such as a

metal has high conductivity and a low resistance.

* An insulator likeglass or avacuum has low conductivity.

* The conductivity of asemiconductor is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or specific frequencies oflight , and, most important, withtemperature and composition of the semiconductor material.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 dissolvedsalts 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.**ome electrical conductivities****Complex conductivity**To analyse the conductivity of materials exposed to alternating electric fields, it is necessary to treat conductivity as a

complex number (or as a matrix of complex numbers, in the case of anisotropic materials mentioned above) called the "admittivity". This method is used in applications such aselectrical impedance tomography , a type of industrial andmedical imaging . Admittivity is the sum of a real component called the conductivity and an imaginary component called the susceptivity. [*http://www.otto-schmitt.org/OttoPagesFinalForm/Sounds/Speeches/MutualImpedivity.htm*]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, seeMathematical descriptions of opacity .**Temperature dependence**Electrical conductivity is strongly dependent on

temperature . Inmetal s, electrical conductivity decreases with increasing temperature, whereas insemiconductor s, electrical conductivity increases with increasing temperature. Over a limited temperature range, the electrical conductivity can be approximated as being directly proportional totemperature . In order to compare electrical conductivity measurements at different temperatures, they need to be standardized to a common temperature. This dependence is often expressed as aslope in the conductivity-vs-temperature graph, and can be used::$sigma\_\{T\text{'}\}\; =\; \{sigma\_T\; over\; 1\; +\; alpha\; (T\; -\; T\text{'})\}$

where

:"σ

_{T′}" is the electrical conductivity at a common temperature, "T′":"σ_{T}" is the electrical conductivity at a measured temperature, "T":"α" is the temperature compensation slope of the material,:"T" is the measured absolute temperature, :"T′" is the common temperature.The temperature compensation slope for most naturally occurring

water s is about 2 %/°C, however it can range between (1 to 3) %/°C. This slope is influenced by thegeochemistry , and can be easily determined in alaboratory .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 .**References****ee also***

Classical and quantum conductivity

*Electrical conduction for a discussion of the physical origin of electrical conductivity.

*Electrical resistance

*Electrical resistivity is the inverse of electric conductivity

*Molar conductivity for a discussion of electrolytic conductivity i.e. conductivity due to ions in solution

*SI electromagnetism units

*Transport phenomena

*Thermal conductivity **External links*** [

*http://glassproperties.com/resistivity/ElectrResistMeasurement.htm Measurement of the Electrical Conductivity of Glass Melts*] Measurement Techniques, Definitions, Electrical conductivity Calculation from the Glass Composition

* [*http://environmentalchemistry.com/yogi/periodic/electrical.html Periodic Table of Elements Sorted by Electrical Conductivity*]

*Wikimedia Foundation.
2010.*

### Look at other dictionaries:

**electrical conductivity**— savitasis laidis statusas T sritis automatika atitikmenys: angl. conductivity; electrical conductivity; specific conductivity vok. spezifischer Leitwert, m rus. удельная проводимость, f; удельная электропроводность, f pranc. conductibilité… … Automatikos terminų žodynas**electrical conductivity**— savitasis elektrinis laidis statusas T sritis chemija apibrėžtis Dydis, atvirkščiai proporcingas savitajai varžai (S/m). atitikmenys: angl. electric conductivity; electrical conductivity rus. удельная электропроводность … Chemijos terminų aiškinamasis žodynas**electrical conductivity**— savitasis elektrinis laidis statusas T sritis fizika atitikmenys: angl. electric conductivity; electrical conductivity vok. spezifische Leitfähigkeit, f; spezifischer Leitwert, m rus. удельная электропроводность, f pranc. conductivité électrique … Fizikos terminų žodynas**Electrical conductivity**— Электрическая проводимость … Краткий толковый словарь по полиграфии**electrical conductivity**— Смотри Электропроводность … Энциклопедический словарь по металлургии**electrical conductivity**— the proportionality constant between current density and applied electric field; a measure of the ease with which a material is capable of conducting an electric current … Mechanics glossary**electrical conductivity**— The ability of a material to conduct electricity. The opposite is resistivity or resistance … Dictionary of automotive terms**Electrical conductivity meter**— An electrical conductivity meter. An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. Commonly used in hydroponics, aquaculture and freshwater systems to monitor the amount of nutrients, salts or… … Wikipedia**Electrical impedance tomography**— (EIT), is a medical imaging technique in which an image of the conductivity or permittivity of part of the body is inferred from surface electrical measurements. Typically conducting electrodes are attached to the skin of the subject and small… … Wikipedia**Electrical conduction**— is the movement of electrically charged particles through a transmission medium (electrical conductor). The movement of charge constitutes an electric current. The charge transport may result as a response to an electric field, or as a result of… … Wikipedia