For more information on cables used to carry electric power, see Electric power . Metals commonly used to make conductors include copper and aluminum. Insulation holds the electricity in the conductors and protects the conductors from damage. Insulation also helps prevent interference. Interference occurs when a conductor picks up stray electricity from other conductors or from the air.
Insulation is made from such nonconducting materials as plastic and paper pulp.
Various types of cables Simple cables are made up of a single pair of insulated wires twisted together. In many cases, multiconductor cables are enclosed in a heavy sheath made up of several layers of aluminum or plastic. Some thick cables also contain steel wire to provide strength. Communications cables are laid underground and along the ocean floor, or they are mounted on poles. Burying cable protects it from harsh weather and keeps the land aboveground uncluttered.