Re: Paralell Conductors
Since you are apparently interested in percentages, the actual resistances (i.e., the type and size of cable) can be left out of the calculation. If all seven wires were the same length, then their resistance would each be, let us say, ?R.? Placing seven of these in parallel gives a total resistance of ?R/7? or about 0.1429R.
Since one wire is longer by 4 feet out of a 40 foot run, its resistance would be 1.1R. The parallel combination of the other six gives a subtotal resistance of ?R/6,? or about 0.1667R. So you wind up with a set of two resistors in parallel, with their values being 1.1R and 0.1667R. That parallel combination gives a new total resistance of 0.1447R (instead of the 0.1429R that equal lengths would have given us). Thus, the total resistance is high by about 1.3%, and the total current would be low by that same 1.3%.
Finally, let?s look at how the seven wires share the load. If all seven were the same length, then each would handle 1/7th (14.29%) of the load current. Instead, you have a current divider, with six wires (resistance of 0.1667R) in parallel with one wire (resistance of 1.1R). The long wire will take on current in the ratio of (0.1667) / (1.1 + 0.1667). This means that the long wire gets 13.16% of the current, instead of the 14.29% that should have been its share. Thus, it is lightly loaded by about 8% (not 40%, sorry Charlie Tuna).