Values for resistance are based on electrical resistivity for copper 1.724 x 10-8 Ω m (0.0174 μΩ m) and electrical resistivity for aluminum 2.65 x 10-8 Ω m (0.0265 μΩ m).• prefixesThe higher the gauge number, the smaller the diameter, and the thinner the wire.Because of less electrical resistance a thicker wire carries more current with less voltage drop than a thinner wire. For longer distances it may be necessary to increase wire diameter - reducing the gauge - to limit voltage drop.