导体通常指电阻率  < 10-4  · cm 的物质。金属和合金一般都是导体，如铝、金、钨、铜、镍铬　　等。能带能隙很小或为 0 , 在室温下电子很容易获得能量而跃迁至导带而导电。-Usually refers to a conductor resistivity 　< 10-4 　cm material. Metals and alloys are generally conductors such as aluminum, gold, tungsten, copper, nickel, chromium and so on. Small band gap or to 0, at room temperature, the easy availability of electronic energy and the transition to the conduction band and electrical conductivity.