Qualified copper wire copper core should be purple, shiny, feel soft. The fake copper core copper wire is purple black, yellow or white, impurities, poor mechanical strength, poor toughness, a little effort that will break, and the wire is often broken. Check, you just peel off the wire 2cm, and then use a piece of paper on the copper core a little rub, if there is a black substance on the white paper, indicating more impurities in the copper core.