Silver conducts 106%, if copper conducts 100%, and whether the current alternates or not, should have no bearing. I believe that there is less resistance at the surface of conductors, so the electrons are taking the path of least resistance, and hence the skin effect. It's more complex than all that, but I'm no theoretician. And just knowing the basics doesn't mean at all that you'll be able to predict which cables will work best in your system before you try them, either.
