An electrical insulatoris a material which does not conduct an electric current. A perfect insulator does not exist, but some materials such as glass, paper, Teflon and ceramics, which have high resistivity, are very good electrical insulators. A much largerclass of materials, even though they may have lower bulk resistivity, are still good enough to insulate electrical wiring and cables. Examples include rubber-like polymers and most plastics. Such materials can serve as practical and safe insulators for low to moderate voltages. Simply stated, most metals are good electrical conductors, most non-metals are not.
Insulators are used in electrical equipment to support and separate electrical wires without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation. The term insulatoris also used more specifically to refer to insulating supports used to attach electric power lines and wires to posts, poles and transmission towers.