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Engineering ToolBox > Conductors

Conductors and conductivity

• Conductors are materials with loosely attached valence electrons - electrons can drift freely between the atoms.
• Insulators have structures where the electrons are bound to the atoms by ionic or covalent bonds - almost no current can flow.
• Semiconductors are insulating materials where the bonds can be broken with applied voltage - electrons can be released and moved from one vacated valence site to another.

Electrical conductivity

Electrical conductivity or specific conductivity is the measure of a material's ability to conduct an electric current. Conductivity is the reciprocal (inverse) of electrical resistivity.

Electrical conductivity is defined as the ratio of the current density to the electric field strength and can be expressed as

 σ = J / E (1)

where

σ = electrical conductivity (1/Ohms m, Siemens/m, SI/m)

J = current density (Amps/m²)

E = electric field strength (Volts/m)