Final answer:
The AC wire that connects to the wide blade of a polarized 2-prong plug is the neutral wire, as it offers a safer, low-resistance path at zero volts relative to the earth.
Step-by-step explanation:
When wiring a polarized 2-prong plug, the AC wire that connects to the wide blade is the neutral wire. The reason for this is because the neutral wire is typically a low-resistance path directly to earth/ground, forcing it to be at zero volts relative to the earth, making it safer to touch if the insulation is missing. This arrangement ensures proper function and increases safety by reducing the risk of electric shock should the insulation around the live wire wear down and make contact with the appliance casing.