ECN Forum Forums Technical Discussion Electrical Theory and Applications Voltage Drop Calcs.

I'm Studying a book Called Electrical Wiring Commerial 13Th. Edition.I've run into a formula for voltage drop.The variable (K)is unknown to me and the book does not reference where, why or how its use has derived.The formula is VD=2xKxDxI/Cm. Does anyone Know of an explicit reference for this (K). Thanx