Diver Dan- In all due respect to your obvious education, I don't know vary many electricians out there that have enough background to use your formula. It certianly is proper for the engineers when an exact voltage drop is calculated, but for the average job out there, most electricians get by very well just by using the simple formula found in any electricians handbook and using Table 8 in Chapter 9 of the NEC. They don't even use Table 9 and consider impedance. Most electricians (myself included) use only the minimum amount of math they have to use to get by. They are in trouble when they have to do voltage drop calculations on Sensitive Electronic Equipment Article 647 Section 647.4(D) where voltage drop limits are in place by code, not optional.
