Conductivity

Conductivity is a measure of a material's ability to conduct electric current. It is commonly denoted by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) and γ (gamma) are sometimes used. The SI unit of conductivity is siemens per meter (S/m).

Definition

Conductivity is the reciprocal (inverse) of electrical resistivity (resistance of a specific specimen of a material), and is measured in siemens per meter (S/m). It is defined as the ratio of the current density (the amount of electric current per unit cross-sectional area) to the electric field strength.

Factors affecting conductivity

Several factors affect conductivity, including the nature of the material, its temperature, the concentration of impurities, and the amount of deformation (strain) to which it has been subjected.

Material

The conductivity of a material is largely determined by the number of free charge carriers (usually electrons) it contains. Metals, which have many free electrons, are good conductors, while most non-metallic solids are poor conductors.

Temperature

In general, conductivity decreases with increasing temperature. This is because as temperature increases, the atoms of the material vibrate more rapidly, which increases the number of collisions between the charge carriers (electrons) and the atoms, impeding the flow of current.

Impurities

The presence of impurities can also affect conductivity. In metals, impurities usually decrease conductivity, while in semiconductors, they can either increase or decrease conductivity, depending on their nature.

Strain

The amount of deformation (strain) a material has been subjected to can also affect its conductivity. When a material is deformed, the arrangement of its atoms is altered, which can affect the number of free charge carriers and their mobility.

Applications

Conductivity is a fundamental property that is used in many areas of science and engineering, including physics, materials science, chemistry, and electrical engineering. It is used in designing and analyzing electrical and electronic circuits, in studying the behavior of semiconductors, and in characterizing materials.

See also

• Electrical resistivity and conductivity
• Electrical conduction
• Electrical resistance and conductance
• Superconductivity

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