Of the metals commonly used for conductors, copper, has a high conductivity. Silver is more conductive, but due to cost it is not practical in most cases. However, it is used in specialized equipment, such as satellites, and as a thin plating to mitigate skin effect losses at high frequencies. Because of its ease of connection by soldering or clamping, copper is still the most common choice for most light-gauge wires.http://en.wikipedia.org/wiki/Electrical_conductorThe most important insulation material is air, but a wide variety of solid insulators are used in electrical apparatus. In transformers, generators, and electric motors with a maximum of 2500 volts to ground between turns, the insulation on the coil wires is a thin coating of varnish so as to get the maximum number of turns in each slot space. Large power transformer windings are still mostly insulated with paper, wood, and silicone oil; although these materials have been used for more than 100 years, they still provide a good balance of economy and adequate performance. Bus bars and circuit breakers in switchgear may be insulated with glass-reinforced plastic insulation, treated to have low flame spread and to prevent tracking of current across the material. In old apparatus made up to the early 1970’s, boards made of compressed asbestos may be used; while this is an adequate insulator at power frequencies, handling or repairs to asbestos material will release dangerous fibers into the air and must be carried out with a high level of precautions. Live-front switchboards up to the early part of the 20th century were made of slate. Electrical power cables may be insulated with polyethylene, crosslinked polyethylene, PVC, rubber-like polymers, oil impregnated paper, Teflon, silicone, fluorinate dethylene propylene, modified ethylene terafluor-ethylene, or even compressed inorganic powder, depending on the application.http://en.wikipedia.org/wiki/Electrical_insulation Compared to copper, aluminium has worse conductivity per unit volume, but better conductivity per unit weight. In many cases, weight is more important than volume making aluminium the ‘best’ conductor material for certain applications. For example, it is commonly used for large-scale power distribution conductors such as overhead power lines. In many such cases, aluminium is used over a steel core that provides much greater tensile strength than would the aluminium alone .Gold is occasionally used for very fine wires such as those used to wire bond integrated circuits to their lead frames. The contacts in electrical connectors are also commonly gold plated or gold flashed (over nickel). Contrary to popular belief, this is not done because gold is a better conductor; it is not. Instead, it is done because gold is very resistant to the surface corrosion that is commonly suffered by copper, silver, or tin/lead alloys. This corrosion would have a very detrimental effect on connection quality over time; gold plating avoids that....
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