juhtuvust

Juhtuvust is a material property that describes how easily electric current can flow through a substance. In scientific terms it is the ability of a material to conduct electricity and is expressed as the conductivity, with the SI unit siemens per metre (S/m). It is the reciprocal of resistivity, and its magnitude spans many orders of magnitude across different materials.

Charge transport responsible for juhtuvust occurs in several ways. In metals, conduction is primarily electronic, driven by free electrons and, to a lesser extent, holes. In ionic conductors such as electrolytes and certain ceramics, ions carry the current. Semiconductors involve both electrons and holes, with conductivity strongly influenced by doping, temperature, and impurities. Some materials exhibit mixed or directional conduction, showing anisotropy in conductivity.

The conductivity σ is governed by the density and mobility of charge carriers. A common relation is σ = nqμ, where n is carrier concentration, q is charge, and μ is mobility. Because different carriers contribute differently, several mechanisms can determine the overall conductivity. Temperature, structure, and composition matter: metallic conductivity typically decreases with rising temperature due to lattice vibrations, while semiconductors and ionic conductors often show increased conductivity with temperature as carrier generation and ion mobility rise.

Measurement and typical ranges vary widely. Conductivity is measured with methods such as four-point probes, impedance spectroscopy for solids, or conductivity meters for liquids. Values span from insulators with extremely low conductivity to highly conductive metals (for example, copper around 5.8×10^7 S/m) or seawater near a few S/m.

Applications of juhtuvust include electrical wiring, electronic devices, energy storage and conversion systems (batteries and fuel cells), sensors, and geophysical studies, where material conductivity reveals composition and structure.