Which two factors determine the amount of voltage a wire is allowed to drop?

• A. Temperature rating and insulation type
• B. Duty cycle and applied voltage
• C. Voltage rating and conductor material
• D. Conductor cross-section and length

Answer: (B)

Voltage drop is governed by how long current flows and the voltage that drives it. In systems with pulsed or intermittent loads, the duty cycle—the fraction of time the circuit is on—determines how much energy is delivered during each cycle, so it directly affects the average voltage drop. The applied voltage sets the baseline amount of potential across the line; higher supply voltage means a larger drop for the same resistance, so the allowable drop scales with it. Put together, these two factors—duty cycle and applied voltage—largely determine how much voltage the wiring is allowed to drop under operating conditions. The wire’s resistance (from length, cross-section, and material) influences the instantaneous drop when the load is on, but the design allowance for drop in a pulsed system centers on duty cycle and applied voltage.