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electric Cable

cables power insulation usually

Cable, electric, insulated conductor used to carry electric power or electric signals. A cable consists of a core conducting metal, usually of several wires twisted or stranded together, surrounded by insulating material. The conducting metal is usually copper, aluminum, or steel. The insulation is most often made of plastic or rubber. Multicore cables contain many cores, each insulated from the others, all contained inside a tube of plastic, rubber, copper, aluminum, or lead, which also serve to keep out moisture and heat. Telephone cables contain several thousand cores. Such cables run along the sea bed between the continents; however, satellite communications are replacing such long cables.

Electric power is distributed by power cables. Inside the home they carry electricity at low power (usually 110 volts). Electricity at high power is carried between cities by overhead cables slung from pylons. The cables do not need insulation around the cores as they are kept far enough apart for the air to act as an insulator and prevent sparking between them, but special glass or ceramic insulators are used to attach them to the pylons. Super-voltage power cables carrying currents at up to about 500,000 volts are usually buried underground and filled with oil or gas, such as nitrogen, to remove heat and increase insulation.

Radio, television, telephone, and other electronic equipment uses low-power signals with high frequencies, requiring a coaxial cable, which has a central core of wire surrounded by insulation, then a sheath of wire braid, and finally an insulating outer covering.

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