Electrical conductivity

Electrical conductivity is the measure of a material's ability to allow the transport of an electric charge. Its SI is the siemens per meter, (A²s³m⁻³kg⁻¹) (named after Werner von Siemens) or, more simply, Sm⁻¹.

It is the ratio of the current density to the electric field strength. It is equivalent to the electrical conductance measured between opposite faces of a 1-metre cube of the material under test.

• The symbol for electrical conductivity is κ (kappa), and also σ (sigma) or γ (gamma).

Electrical conductance is an electrical phenomenon where a material contains movable particles with electric charge (such as electrons), which can carry electricity. When a difference of electrical potential is placed across a conductor, its electrons flow, and an electric current appears.

A conductor such as a metal has high conductivity, and an insulator like glass or a vacuum has low conductivity. A semiconductor has a conductivity that varies widely under different conditions.

Electrical conductivity is the reciprocal (or inverse) of electrical resistivity.

Electrical Conductivity Media

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  A piece of resistive material with electrical contacts on both ends

• An animation of Newton's cradle. Like the balls in Newton's cradle, electrons in a metal quickly transfer energy from one terminal to another, despite their own negligible movement.

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  Original data from the 1911 experiment by Heike Kamerlingh Onnes showing the resistance of a mercury wire as a function of temperature. The abrupt drop in resistance is the superconducting transition.

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  Lightning is an example of plasma present at Earth's surface. Typically, lightning discharges 30,000 amperes at up to 100 million volts, and emits light, radio waves, and X-rays. Plasma temperatures in lightning might approach 30,000 kelvin (29,727 °C) (53,540 °F), and electron densities may exceed 1024 m−3.