Electrical conductor

Essentially what is occurring is a long chain of momentum transfer between mobile charge carriers; the Drude model of conduction describes this process more rigorously.

This momentum transfer model makes metal an ideal choice for a conductor; metals, characteristically, possess a delocalized sea of electrons which gives the electrons enough mobility to collide and thus affect a momentum transfer.

Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents.

This formula is not exact: It assumes the current density is totally uniform in the conductor, which is not always true in practical situation.

Similarly, if two conductors are near each other carrying AC current, their resistances increase due to the proximity effect.

Temperature affects conductors in two main ways, the first is that materials may expand under the application of heat.

A phonon is essentially a lattice vibration, or rather a small, harmonic kinetic movement of the atoms of the material.

Much like the shaking of a pinball machine, phonons serve to disrupt the path of electrons, causing them to scatter.

[3] Because of its ease of connection by soldering or clamping, copper is still the most common choice for most light-gauge wires.

However, it is used in specialized equipment, such as satellites, and as a thin plating to mitigate skin effect losses at high frequencies.

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.

As aluminum is roughly one-third the cost of copper by weight, the economic advantages are considerable when large conductors are required.

Its larger coefficient of thermal expansion than the brass materials used for connectors causes connections to loosen.

These effects can be mitigated with suitably designed connectors and extra care in installation, but they have made aluminum building wiring unpopular past the service drop.

In North America, conductors are measured by American wire gauge for smaller ones, and circular mils for larger ones.