864. Why does copper conduct electric currents better than steel and lead? Why do copper and aluminum seem to conduct about the same? - L
A metal's conductivity is related to how far an electron can coast through the metal before suffering a collision that reduces its kinetic energy. Since an electron can collide with an impurity in the metal or a region of local disorder, the first task in obtaining a good conductor is to make a pure and uniform metal. Increased temperature also enhances these inelastic collisions, so keeping a metal cool improves its conductivity. Finally, different metals exhibit different couplings between the electrons and the metal ions from which those electrons came. Copper and aluminum have relatively weak electron-ion couplings while steel and lead have stronger couplings. The stronger the coupling, the more likely is a collision between an electron and an ion. Because of their weaker couplings, the electrons in copper and aluminum suffer far fewer collisions per centimeter than the electrons in steel and lead. That's why copper and aluminum are better conductors of electricity than steel and lead. The coupling in copper is only slightly weaker than that in aluminum, so they have similar conductivities. However, aluminum's tendency to form a very hard, insulating oxide coating (aluminum oxide or "alumina" is the mineral sapphire) makes it a bit tricky to use in wiring.