Conduction

Name:
Conduction
Detailed information:
(1) Transfer of heat through a substance or from one substance to another when the two substances are in physical contact (thermal conduction). Crystalline solids (especially metals and alloys) are good thermal conductors; liquids such as water and glass and high polymers such as rubber and cellulose usually are not.(2) Transfer of an electric current through a solid or liquid (electrical conduction). In metallic or electronic conductors the current is carried by a flow of electrons, the atomic nuclei remaining stationary. This type of conduction is common to all metals and alloys, carbon and graphite, and certain solid compounds (manganese dioxide, lead sulfide). In electrolytic or ionic conductors the current is carried by ions, as in solutions of acids, bases, and salts and in many fused compounds. In electrolytic conduction, as in metallic conduction, heat is generated and a magnetic field is formed around the conductor; a transfer of matter also occurs. In a few materials, such as solutions of alkali and alkaline earth metals in anhydrous liquid ammonia, both types of conduction take place simultaneously; such conductors are called mixed conductors. See Semiconductor; Transference Number.