Electric Conductor

Electrical energy is transmitted by metal conductors. Wires are usually soft and flexible. They may be bare, or coated with flexible insulating material. In most cases, they have a circular cross-section. Cables have larger cross-sections than wires, and they are usually stranded, built up as an assembly of smaller solid conductors. Cords are small-diameter flexible cables that are usually insulated. Multi-conductor cable is an assembly of several insulated wires in a common jacket. Bus-bars are rigid and solid, made in shapes like rectangular, rods or tubes, and are used in switchboards.

Most conductors are made from copper or aluminum, which are both flexible materials. While copper is a better conductor, aluminum is cheaper and lighter. For overhead lines the conductors are made with a steel or aluminum-alloy core, surrounded by aluminum. The conductors are supported on insulators, which are usually ceramic or porcelain. They may be coated with rubber, polyethylene, asbestos, thermoplastic, and varnished cambric. The specific type of the insulating material depends on the voltage of the circuit, the temperature, and whether the circuit is exposed to water or chemicals.