An electrical cable is a bundle of wires which are used for transmitting electricity. It is typically insulated with some form of material to prevent it from catching fire and also to protect it from being damaged by chemicals in the air. There are a number of different types of cables which are used for a variety of purposes.
The basic type of cable is based on the number of wires it contains, and how it is terminated at its ends (by connectors). In residential circuits, two-conductor cables are often used, with each insulated wire containing one conductor and a ground wire. Three-conductor cables are more common in commercial and industrial applications.
In some cases, a single conductor is combined with another conductor in a twisted pair, to reduce energy dissipation and improve interference. These are often called coaxial cables and have been in use since World War II.
Some of these cables have several layers of insulation to keep the conductors separated from each other and to prevent unintended current flow, or short-circuiting. Various synthetic polymers are used for this purpose.
A layer of water-proofing is usually added to ensure that the cable does not become contaminated by rain, snow or other forms of liquids. This is usually a thin plastic sheath. In some cases, the sheath is made from aluminum foil.
There are also a number of cables which have been designed for extreme conditions. This can include steel mills and boiler rooms (high temperature), on mobile equipment (vibration and flexing), in chemical plants (corrosion), near nuclear reactors (high radiation), or on artificial satellites (pressure extremes).
The main materials of power cables are copper and aluminium. These are stable in performance at high temperatures and have good corrosion resistance. Some of these cables are stranded to add flexibility while maintaining their electrical strength.
Other common cables are multi-conductor ribbon or flat cables, which have many wires in a continuous stripe that is crimped into a connector. This is a more convenient way of connecting many wires than individually terminating each one, and is especially useful when the cable must be terminated quickly.
Some of these cables are flexible and can withstand continuous bending. These are commonly used in computer disk drives and telephone wiring.
Terminal blocks and barrier strips are another type of connector which is used to connect individual wires without splicing them together. These connectors are available in a variety of terminals, and can be adapted to fit almost any size of wire.
Termination methods include soldering, insulation displacement, insulating piercing, screw clamping, axial screw termination, cage clamping, and crimping. Some of these methods require specialized tools, but they can be very efficient and make repairs quicker and easier.
Some cables are tinned, or coated with a tin-lead alloy to provide additional protection from corrosion and to increase conductivity. Other types are coated with tin-nickel or nickel-chromium to provide extra conductivity and resist heat. These cables are usually more expensive than other types, but are used in many different applications.