Metals are good conductors of electricity and heat (copper, aluminium, gold, iron,…). Other conductors are graphite, solutions of salts, and all plasmas.
All conductors contain movable electric charges which will move in the electric field so that they conduct electric current.
Semiconductors
Semiconductors are very similar to insulators but it is possible to control their electrical properties (silicon, germanium, gallium arsenide,…) The behaviour of a semiconductor can be easily manipulated by the addition of impurities, known as doping and semiconductor conductivity can be controlled by introduction of an electric field, by exposure to light, magnetic field and even pressure and heat.
Insulators = dielectrics
An insulator is a material that resists the flow of electric current. Dielectric materials can be solids, liquids, or gases; paper, porcelain, glass, and most plastics, distilled water, air, nitrogen, vacuum etc. are dielectrics
Magnets
A magnet is a material or object that produces a magnetic field.
Ferromagnetic materials are the 'popular' perception of a magnet. These materials can retain their own magnetization (Fe, Co, Ni, metal alloys…)
Superconductors
The resistance of a superconductor, on the other hand, drops abruptly to zero when the
material is cooled below its "critical temperature". Superconductors have exactly zero
resistivity when there is no magnetic field present (tin, aluminium, various metallic alloys
and some heavily-doped semiconductors).
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