Which factor most directly influences voltage drop in conductor sizing?

• A. Length only
• B. Conductor color
• C. Impedance, length, and current
• D. Insulation type only

Answer: (C)

Voltage drop along a conductor is driven by the current flowing through it and the opposition the path offers, i.e., its impedance. The basic relation is ΔV = I × Z, so how much voltage drops depends on the current and the conductor’s impedance. Impedance accounts for resistance and reactance, and both resistance and thus Z grow with longer runs and with smaller cross-sectional area. More current increases the drop directly, and a longer conductor increases the impedance the current sees. That’s why you need to consider impedance, length, and current together when sizing conductors. The color of the conductor or the insulation type doesn’t directly change the voltage drop in normal sizing, so they aren’t the determining factors by themselves.