conductivitate

Conductivitate, the Romanian term for electrical conductivity, is the property of a material that describes how readily electric current can flow through it. In physics it is quantified by the conductivity σ, measured in siemens per meter (S/m), and is the reciprocal of resistivity (ρ). Higher conductivity means easier current flow, while low conductivity indicates better insulation.

Conductivity depends on temperature, composition, and structure. Metals typically have high conductivity due to freely moving electrons; electrolytes conduct through mobile ions; semiconductors have conductivity that can be tuned by impurities (doping) and temperature. Some materials exhibit anisotropy, where conductivity varies with direction; in alternating current, conductivity is frequency dependent and becomes a complex quantity, with a real part representing dissipative transport and an imaginary part associated with energy storage.

Measuring conductivity involves different methods: a four-point probe for solids, conductivity meters for liquids, and electrochemical impedance spectroscopy to study frequency response. Practical values vary widely across materials and conditions. For example, copper is around 6.0 × 10^7 S/m, distilled water about 5 × 10^-6 S/m, seawater roughly 5 S/m, and glass typically in the 10^-12 to 10^-10 S/m range.

Applications rely on conductivity properties to enable or inhibit current flow, including power transmission, electronic components, sensors, energy storage materials, and protective barriers in insulating systems.