How can I tell which electrical wire is “hot”?
There are other ways to mark a neutral. The most common is a white wire, and next I would say is being ribbed as you say. Look for any difference between the two wires (there are more ways they can be marked than I care to list here). Could be white marks of some sort, even one conductor being tinned and not the other, for example. If you put the difference you see in this question I could tell you which is which. If you cannot see any difference, then you can test it. Even if you knew what marking was used, it might be a good idea to verify it. Use a continuity tester to see which wire is connected where on the lampholder. The neutral is connected to the screw shell and the hot is connected to the tab at the bottom that contacts the tip of the light bulb. For completeness, the neutral is the wider blade on the polarized plug.
