The conduction of electricity through a material is the transference of an electrical charge from one position to another. The charge may be transferred by movement of electrons, or by the migration of ions. Conduction in metals is due to electron migration, but it is the movement of ions that is responsible for the conductivity of electrolytes and for the very low conductivities observed in some insulating materials. In the class of materials known as semiconductors charge is carried by the motion of electrons and the movement in the opposite direction of positive ‘holes’.
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