Resistivity and conductivity

A uniform conductor with a length of L and a cross-sectional area of ​​S, with a voltage V applied to both ends, will have a current flowing through it, which is called conductivity.

According to Ohm's law, R is not only related to the properties of the material, but also to the length L and cross-sectional area S of the material. The resistivity p characterizes the properties of the material itself and can be used to characterize the conductivity of the material. According to the different resistivities, materials can be divided into conductors, insulators and semiconductors. The resistivity of conductors is less than 10-3Ω·m, the resistivity of semiconductors is 10-3~1010Ω·m, and the resistivity of insulators is greater than 109Ω·m

Conductivity σ (unit: Ω-1·m-1) is another parameter that characterizes the conductivity of materials, and its relationship with resistivity ρ is σ=1/ρ

The unit of conductivity can also be written as S/m (Si/m), and sometimes it is also expressed as relative conductivity IACS%.

IACS% definition: Taking the conductivity of the international standard pure soft copper (room temperature 20℃, resistivity 0.01724 Ω·mm2/m) as 100%, the percentage of the conductivity of other conductive materials compared with it is the relative resistivity of the conductive material. The IACS% of Fe is 17%, and that of A1 is 65%.