Insulator, << IHN suh `lay` tuhr, >> Electric, is a material that conducts almost no electricity. Insulators, also called dielectrics, are used to prevent electric current from flowing into places where it would be undesirable or dangerous. Such materials as dry wood, glass, mica, plastics, and rubber are insulators. Dry air and certain oils may also serve as insulators.
An insulator conducts electric current poorly because its electrons are bound so tightly to their nuclei that they cannot move freely from atom to atom. Therefore, when an insulator is connected to a battery or other source of electric energy, not enough electrons move through the insulator to produce a current. In contrast, materials called conductors, which include such metals as aluminum, copper, and silver, have electrons that are weakly bound to their nuclei. These electrons travel freely, resulting in a flow of electricity. Materials called semiconductors also have relatively low resistance to current flow. Semiconductors, such as germanium and silicon, conduct electricity better than insulators but not as well as conductors.
Insulators are used in many kinds of electrical and electronic equipment. For example, metal wires and cables that conduct electricity from power plants to homes and offices are covered with insulating materials to prevent the leakage of current. Insulators are also used in capacitors to increase their ability to store an electric charge (see Capacitor ). When working around high-voltage equipment, electricians use tools with plastic or rubber handles and wear rubber-soled shoes to avoid injury from electric shock.
