Define electrical conductivity of a conductor and give its S.I. unit. On what factors does it depend ?

Electrical conductivity, also known as specific conductivity or simply conductivity, is a measure of a material's ability to conduct an electric current. It quantifies how easily electric charge carriers, typically electrons, can move through a material when subjected to an electric field. In simpler terms, it reflects how well a substance allows electricity to flow through it.

The SI (International System of Units) unit for electrical conductivity is Siemens per meter (S/m).

Factors that affect the electrical conductivity of a conductor include:

Temperature: Generally, as the temperature of a conductor increases, its electrical conductivity decreases. This is due to increased thermal motion of the charge carriers (usually electrons) which hinders their ability to move freely.

Material: Different materials have different inherent electrical conductivities. Metals, such as copper and silver, are known for their high electrical conductivity, while insulators, like rubber or plastic, have very low electrical conductivity. Semiconductors, like silicon, have intermediate conductivity.

Cross-Sectional Area: The cross-sectional area of the conductor also plays a role. A larger cross-sectional area allows for more charge carriers to flow through, increasing the overall conductivity.

Length: The length of the conductor affects conductivity as well. Longer conductors tend to have higher resistance and lower conductivity compared to shorter ones, assuming the same material and cross-sectional area.

Purity: Impurities and defects within a material can impede the flow of charge carriers, reducing electrical conductivity. Highly pure materials exhibit better conductivity.

Crystal Structure: The arrangement of atoms in a crystalline lattice can influence electrical conductivity. In some materials, the crystal structure can promote the movement of charge carriers.

Doping: In semiconductors, intentional introduction of impurities (doping) can significantly alter their electrical conductivity. N-type doping adds extra electrons, increasing conductivity, while P-type doping creates "holes," increasing resistance.

Frequency: In some cases, especially with high-frequency alternating current (AC) signals, the electrical conductivity of a material may vary with frequency due to skin effect or other electromagnetic phenomena.

In summary, electrical conductivity measures a material's ability to conduct electricity, and it depends on factors such as temperature, material properties, cross-sectional area, length, purity, crystal structure, doping, and frequency. These factors determine how easily electric charge can flow through a conductor, with high conductivity indicating efficient electrical conduction.