What formula calculates voltage drop, and how do allowable values differ between lighting and other low-voltage applications?

Voltage drop is computed using \( Vd = \frac{mV/A/m \times l \times Ib}{1000} \), where \( mV/A/m \) represents voltage drop per meter per amp, \( l \) is conductor length, and \( Ib \) denotes design current. For public low-voltage systems, permissible limits are 3% for lighting circuits versus 5% for general applications, balancing performance requirements with energy efficiency standards.