Dumb question... I got some 14g speaker wire from Home Depot and noticed that one strand of wire is all copper, and the other is copper mixed with some other type of material..silver colored..no idea what it is. 1st question is..why isn't this 100% copper on both strands? 2nd question..which side is the + and which is the -? The wire is not marked, I'm assuming the 100% copper strand is the +. Thanks!