If wired properly the ridged wire is the neutral.
The ribbed sheathing always denotes the neutral conductor and should be connected to the neutral incoming power conductor (usually white). The non-ribbed sheathing is the hot conductor and should be connected to the hot incoming power conductor (generally black). It will work if wired backward (reverse polarity), but if the appliance is polarized, you should wire it accordingly. For example, a light socket is generally polarized to make the ribbed socket part (which human hands will likely come in contact with) neutral. Wiring with reverse polarity would make this socket hot (not safe).
In an electrical circuit, the white wire is typically used as the neutral wire, not the hot wire.
In electrical wiring, the live or "hot" wire is typically brown or red, the neutral wire is typically blue or black, and the ground wire is yellow or green. So, in this case, the brown wire is likely the hot wire, the blue wire is the neutral wire, and the yellow green wire is the ground wire.
An extension cord that you plug into your house is neither positive OR negative. It uses alternating current so there's a live wire and a ground. Only direct currents (like those in cars) have positive and negative. On a two wire extension cord the ribbed side is the neutral. If you look close and it is a moulded plug on the end of the extension cord you will find that the side with the rib is also the same side as the wider blade on the plug. This corresponds to the wide blade hole in the receptacle which is also the neutral side of the receptacle.
The black wire is typically hot, while the white wire is neutral.
How do you determine what? If you are asking how do you measure the voltage between Hot and Neutral, I suggest a voltmeter. If you are asking how do you differentiate between Hot and Neutral in home wiring, the Hot is Black and Neutral is White.
If a "hot" wire contacts the "neutral" or ground wire, electrical current flows to the ground.
In an electrical circuit, the white wire is typically designated as the neutral wire.
In an electrical circuit, the black wire is typically the hot wire.
Red is hot Green is ground White is neutral
In an electrical circuit, the white wire is typically considered to be the neutral wire.
In an electrical circuit, the white wire is typically used as the neutral wire.