so I was having this discussion with an old timer and he said in the course of our conversation that ac current has no polarity and another in the talk said well why is so much then made of a wire configuration and I added there is a wall plug tester for the order of the wires in a socket this all came about when adding new input ac 110 v cables to a small 100 amp hobby welder and by industrial standards this is no big unit but on old house wiring and the 50 ft. lead it seems to make a difference as to the grade of wire and how many plugs are on the cord so running two 16 ga. cords side by side one for blk. and one for wht. wired directly to the field coils inside the welder then to the boxes breaker panel works well enough the question it which leg should the switch be i've heard some off brand products can be and are often wired wrong also dose the blk. provide the bulk of the current or the wht. leg as the wht. is the bigger prong on the plug and plug in with a light bulb I can easily dismiss the need for a correct wire hook up as for a amp draw of 20+ amps there seems to be a need for a more closely followed format dosn't the switch spark in side if wired to the load side like in dc or is there really no diff