A cable is made up of a number of wires, running alongside each other and twisted together to form a single unit. Cables can be made of a variety of materials, each with different properties, and therefore suited to different purposes.
The aluminium cable is one of the main electrical cables, and is a competitor to the copper cable. The aluminium cable has two advantages over copper: aluminium is cheaper than copper, and it is also lighter. Generally, one pound of aluminium can equal the current carrying capacity of two pounds of copper. The lower weight of aluminium cables is a clear advantage in building overhead power lines and in the construction of aircraft, two of the main usages for aluminium cables.
Despite the higher price, copper does have advantages over aluminium, particularly with regard to safety. Copper has greater ductility than aluminium, and is also less susceptible to electrical contact problems, and therefore copper offers a greater margin of safety.
Due to its greater flexibility, copper cables can be made much thinner than aluminium cables, making them better suited to some purposes and also making them easier to install. For this reason, copper is a common material in telecommunications and electrical circuitry.
Copper and aluminium covers the main two types of cable used in electrical engineering, but cable is also used extensively for mechanical and construction purposes. Cables used for these purposes are often required to support considerable weight, and so strength is a much more important qualification than with electrical cabling. To meet this need, cables are formed by twisting several strands of metal into a helix shape. This variety of cable is usually made of steel.
Steel cables are used in construction for purposes such as supporting suspension bridges, or free standing structures such as radio masts and wind turbines. They are used in engineering for the transmission of mechanical power, such as in cranes or elevators.
Optical Fibre Cables
Outside of electrical and mechanical purposes, cables can also be used for data transmission. Optical fibre cables contain numerous optical fibres that are used to carry light. Optical fibre cables are the fastest available way of transferring data, as they transmit at the speed of light in glass, which is approximately 200,000 kilometers per second.