In an extension cord with two pin plugs, I saw that one of the wires has a ribbing on the plastic sheath but the other wire sheathing is smooth. I was told that one is the hot wire and the other the neutral. Which is which? I saw that the 'ribbed' wire is connected to the wider of the two pins and the smooth wire is attached to the narrower pin. Does this mean the wider pin is the 'hot' pin?

thank you...