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TL;DR

Master voltage drop formulas, acceptable limits, and conductor sizing adjustments for long circuit runs. Voltage drop calculations ensure equipment operates within rated parameters and are frequently tested.

By Valenke Exam Prep Team·Last updated 2026-06-03

Free Voltage Drop Calculations Practice Questions

Journeyman Electrician License Exam · Electrical Theory & Trade Math

This module covers Voltage Drop Calculations as part of the Electrical Theory & Trade Math section, testing your understanding of core concepts and their practical application.

ExamJourneyman Electrician License Exam
Pass Rate55%
Duration240 minutes
ModuleVoltage Drop Calculations

Why Voltage Drop Calculations matters

Voltage Drop Calculations is one of the most tested areas because medication errors are among the most preventable causes of patient harm.

Sample Practice Questions (5)

1. The NEC recommends that the voltage drop for a branch circuit should not exceed what percentage of the applied voltage?

  • 5%
  • 3%
  • 10%
  • 2%

2. In the voltage drop formula, the multiplier for a single-phase circuit is 2, while the multiplier for a three-phase circuit is:

  • 3
  • 1.732
  • 1.414
  • 2.5

3. A single-phase, 120V circuit uses 12 AWG copper conductors (6,530 CM) to supply a 16A load located 100 feet from the panel. What is the voltage drop?

  • 6.33V
  • 3.16V
  • 12.66V
  • 5.19V

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4. A three-phase, 208V circuit uses 10 AWG copper conductors (10,380 CM) to supply a 20A load 200 feet from the panel. What is the approximate voltage drop?

  • 4.30V
  • 8.61V
  • 9.94V
  • 14.90V

5. A single-phase, 240V branch circuit uses 6 AWG copper conductors (26,240 CM) and carries 40A over a distance of 175 feet. What is the percentage voltage drop, and does it comply with the NEC 3% branch circuit recommendation?

  • 1.43% — complies
  • 5.73% — does not comply
  • 2.87% — complies
  • 3.44% — does not comply

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Frequently Asked Questions

How many Voltage Drop Calculations questions are on the Journeyman Electrician License Exam?▼
The Electrical Theory & Trade Math section, which includes Voltage Drop Calculations, typically represents a significant portion of the exam. Focus on understanding core concepts rather than memorizing exact question counts, as the exam uses adaptive testing.
What is the best way to study Voltage Drop Calculations?▼
Practice solving calculation problems daily rather than just reading formulas. Work through problems step-by-step, check your units, and time yourself to build speed and accuracy under exam conditions.
What topics within Voltage Drop Calculations should I focus on most?▼
Focus on the concepts that appear in our practice questions and any areas where you consistently score below 70%. The adaptive practice mode will automatically target your weak areas for efficient study.