Single-phase system:
\[ V_{\text{Drop}} = \frac{2 \times Z \times I \times L}{1000} \]
Three-phase system:
\[ V_{\text{Drop}} = \frac{1.73 \times Z \times I \times L}{1000} \]
Impedance (Z): The opposition that a conductor offers to the flow of current, measured in ohms per 1,000 feet.
Load Current (I): The amount of current flowing through the circuit, measured in amperes.
Length (L): The length of the conductor, measured in feet.
Assume a single-phase 120V circuit carries a current of 30A, where the conductor impedance is 1.5 ohms per 1,000 feet, and the circuit length is 75 feet.
Voltage drop:
\[ V_{\text{Drop}} = \frac{2 \times 1.5 \times 30 \times 75}{1000} = 6.75 \text{ V} \]
Percentage voltage drop:
\[ \text{Percentage Voltage Drop} = \frac{6.75}{120} \times 100 = 5.63\% \]