Copperhas been used in electricalwiringsince the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand forcopper wireas an electricalconductor. Copperand its alloys are also used to make electrical contacts.

Aluminumconductors are larger in size than equal ampacity copper conductors. However, with the compact conductors normally used foraluminumalloy buildingwire, conduit sizing is generally the same for equal ampacity copper andaluminum.