Any material that conducts heat or electricity (as opposed to an insulator, or nonconductor). A good conductor has a high electrical or heat conductivity, and is generally a substance rich in loosely-held free electrons, such as a metal. Copper and aluminium are good conductors. A poor conductor (such as the non-metals glass, porcelain, and rubber) has few free electrons and resists the flow of electricity or heat. Carbon
is exceptional in being non-metallic and yet (in some of its forms) a relatively good conductor of heat and electricity. Substances such as silicon
, with intermediate electrical conductivities that are improved by heat, light, or impurities, are known as semiconductors
Liquids (including water) can also be electrical conductors. Electricity (current) can flow by the movement of charged ions through a solution or a molten salt (electrolyte). This process is called electrolysis.
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