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Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. [1] [2] The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor. [3] Copper is the electrical conductor in many categories of electrical wiring.
Famously, 14,700 short tons (13,300 t) of silver on loan from the United States Treasury were used in the making of the calutron magnets during World War II due to wartime shortages of copper. [ 4 ] Aluminum wire is the most common metal in electric power transmission and distribution .
Copper wires in a cable may be bare, or they may be plated with a thin layer of another metal, most often tin but sometimes gold, silver or some other material. Tin, gold, and silver are much less prone to oxidation than copper, which may lengthen wire life, and makes soldering easier. Tinning is also used to provide lubrication between strands.
Since copper is an excellent thermal and electrical conductor among engineering metals (second only to silver), [149] electrical systems that utilize copper generate and transmit energy with high efficiency and with minimum environmental impacts.
Streetcars created enormous demand for early electricity. This Siemens Tram from 1884 required 500 V direct current, which was typical. Much of early electricity was direct current, which could not easily be increased or decreased in voltage either for long-distance transmission or for sharing a common line to be used with multiple types of electric devices.
Power cables use stranded copper or aluminum conductors, although small power cables may use solid conductors in sizes of up to 1/0. (For a detailed discussion on copper cables, see: Copper wire and cable.). The cable may include uninsulated conductors used for the circuit neutral or for ground (earth) connection.
In comparing the performance of silver and gold since 1925, Johnson notes: “At the end of 1925, the price of an ounce of gold was $20.63. At the end of 2020, an ounce of gold sold for $1,893.66.
Coaxial cable, or coax (pronounced / ˈ k oʊ. æ k s /), is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric (insulating material); many coaxial cables also have a protective outer sheath or jacket.