What is voltage drop and when is it a concern?

• A. Voltage drop is the loss of voltage along a conductor due to resistance; it's a concern for long runs or high-current circuits.
• B. Voltage drop is the increase in voltage along a conductor due to resistance.
• C. Voltage drop is the total voltage supplied by the utility.
• D. Voltage drop is the voltage difference between two points along a conductor when idle.

Answer: (A)

Voltage drop is the loss of voltage that occurs along a conductor as current flows through its resistance. When current travels through wire, some energy is dissipated as heat, so the voltage available at the far end of the run is lower than the supply. The amount of drop follows V = I × R, so longer runs or higher current increase the drop. This matters because if the voltage at the load gets too low, equipment may not operate correctly—lights may dim, motors may run slowly or overheat, and electronic devices can malfunction. To keep performance acceptable, engineers limit voltage drop to a small percentage of the supply (commonly around 3% for feeders and up to 5% for branch circuits) by using larger conductors, shorter runs, or distributing the load. The other descriptions describe increasing voltage, the total utility supply, or an idle difference, none of which match what voltage drop represents.