Free Electrician Practice Test: 15 NEC 2023 Questions
This free electrician practice test contains 15 multiple-choice questions based on the National Electrical Code (NEC) 2023. No sign-up is required. Each question includes an instant explanation and the exact NEC article so you know exactly where to look in the code book. The questions cover topics that appear regularly on journeyman and master electrician licensing exams across all 50 states.
Topics Covered in This Test
How This Practice Test Works
- 1.Read the question and select your answer from the four choices.
- 2.Click Check Answer to see whether you got it right, along with the NEC code explanation and a breakdown of why each wrong answer is incorrect.
- 3.Click Next Question to advance. After question 15, you will see your score and a per-question breakdown.
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In a dwelling unit kitchen, which receptacles require GFCI protection under NEC 2023?
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All 15 Questions, Answers, and Explanations
Prefer to read through the full answer key? Every question from the practice test is below with the correct answer, the NEC 2023 citation, and an explanation of why each other choice is wrong. Tap a question to expand it.
Question 1: In a dwelling unit kitchen, which receptacles require GFCI protection under NEC 2023?
- A.Only receptacles within 6 feet of a sink
- B.All receptacles serving countertop surfaces
- C.Only receptacles on 20-ampere circuits
- D.Only receptacles installed after 2014
Correct answer: B. All receptacles serving countertop surfaces. NEC 210.8(A)(6) requires GFCI protection for all receptacles that serve kitchen countertop surfaces in dwelling units, not just those within 6 feet of a sink. The 2023 NEC expanded GFCI requirements significantly. If a receptacle could be used on a countertop, it must be GFCI-protected.
Why the other choices are wrong
- A.The old rule referenced 6 feet from a sink. The 2023 NEC now requires GFCI for all countertop receptacles regardless of distance.
- C.Circuit amperage does not determine GFCI requirements. Both 15A and 20A circuits require GFCI in kitchens.
- D.GFCI requirements apply based on location and use, not installation date.
Question 2: What is the ampacity of a 12 AWG THWN copper conductor in a conduit containing 3 current-carrying conductors, using the 75°C column of NEC Table 310.16?
- A.15 amperes
- B.20 amperes
- C.25 amperes
- D.30 amperes
Correct answer: C. 25 amperes. Per NEC Table 310.16, 12 AWG THWN copper reads 25 amperes in the 75°C column (THWN is a 75°C-rated insulation). With only 3 current-carrying conductors in the raceway, no adjustment factor applies, so the table value of 25 amperes stands. Keep the OCPD rule separate: 240.4(D) still caps the breaker for 12 AWG copper at 20 amperes, but the question asks for the Table 310.16 ampacity, not the overcurrent device size.
Why the other choices are wrong
- A.15 amperes is the 60°C column value for 14 AWG copper, not 12 AWG.
- B.20 amperes is the 60°C column value for 12 AWG copper, and the 240.4(D) breaker limit, but the 75°C column value the question asks for is 25 amperes.
- D.30 amperes is the 90°C column value for 12 AWG copper (or the 75°C value for 10 AWG), not the 75°C value for 12 AWG.
Question 3: Per NEC Table 314.16(B), each 14 AWG conductor adds how many cubic inches to box fill calculations?
- A.1.5 cubic inches
- B.2.0 cubic inches
- C.2.25 cubic inches
- D.2.5 cubic inches
Correct answer: B. 2.0 cubic inches. NEC Table 314.16(B) assigns a volume allowance of 2.0 cubic inches per 14 AWG conductor. Box fill calculations prevent overcrowding that could damage insulation. You count each conductor entering the box, plus double count for devices (receptacles, switches), and add one count for all equipment grounding conductors combined.
Why the other choices are wrong
- A.1.5 cubic inches is not a standard Table 314.16(B) value for any conductor size.
- C.2.25 cubic inches is the allowance for 12 AWG conductors, not 14 AWG.
- D.2.5 cubic inches is the allowance for 10 AWG conductors.
Question 4: A branch circuit supplies a continuous load of 16 amperes. What is the minimum required branch circuit rating?
- A.16 amperes
- B.18 amperes
- C.20 amperes
- D.25 amperes
Correct answer: C. 20 amperes. NEC 210.19(A)(1) requires that branch circuit conductors have an ampacity not less than 125% of the continuous load. 16A × 125% = 20A. This is the 125% continuous load rule, one of the most-tested code calculations on the exam. A 20A rated circuit is the minimum that can legally supply a 16A continuous load.
Why the other choices are wrong
- A.16A would only be acceptable for a non-continuous load. Continuous loads (3+ hours) require 125% sizing.
- B.18A is not a standard overcurrent device rating and does not satisfy the 125% rule.
- D.25A exceeds the minimum requirement. The minimum is 20A (125% of 16A).
Question 5: What is the minimum ampere rating required for the service disconnecting means of a one-family dwelling under NEC 230.79(C)?
- A.60 amperes
- B.100 amperes
- C.150 amperes
- D.200 amperes
Correct answer: B. 100 amperes. NEC 230.79(C) establishes 100 amperes as the minimum service disconnect rating for a one-family dwelling. This is a hard floor regardless of the calculated load. The service disconnect must be rated at least 100A even if the calculated load is lower.
Why the other choices are wrong
- A.60A is the minimum for small loads in other occupancy types, not one-family dwellings.
- C.150A exceeds the minimum, it may be the actual installed size but is not the code minimum.
- D.200A is commonly installed but is not the minimum required by NEC for a single-family dwelling.
Question 6: Using NEC Table 220.12, what is the general lighting load (in VA per square foot) for a dwelling unit?
- A.1 VA per sq ft
- B.2 VA per sq ft
- C.3 VA per sq ft
- D.4 VA per sq ft
Correct answer: C. 3 VA per sq ft. NEC Table 220.12 assigns 3 VA per square foot for dwelling units. This is the starting point for nearly every residential load calculation. Multiply the square footage of the living area by 3 VA, then apply demand factors from Table 220.42 when calculating feeder or service size.
Why the other choices are wrong
- A.1 VA/sq ft applies to storage warehouses, not dwellings.
- B.2 VA/sq ft is not a listed dwelling value in Table 220.12.
- D.4 VA/sq ft applies to office buildings under the optional method, not dwellings.
Question 7: When installing 3 or more conductors in a conduit or tubing, what is the maximum allowable fill percentage per NEC Chapter 9, Table 1?
- A.31%
- B.38%
- C.40%
- D.53%
Correct answer: C. 40%. NEC Chapter 9, Table 1 limits conduit fill to 40% of the cross-sectional area when 3 or more conductors are installed. One conductor = 53%, two conductors = 31%, and 3+ conductors = 40%. Exceeding fill limits creates excessive heat buildup and makes pulling conductors nearly impossible.
Why the other choices are wrong
- A.31% is the maximum fill for exactly 2 conductors, not 3 or more.
- B.38% is not listed as a standard fill percentage in NEC Chapter 9, Table 1.
- D.53% is the maximum fill for a single conductor only.
Question 8: Type NM cable must be secured within what distance of every cable entry into a box, cabinet, or fitting?
- A.6 inches
- B.8 inches
- C.12 inches
- D.18 inches
Correct answer: C. 12 inches. NEC 334.30(A) requires NM cable to be secured within 12 inches of every box, cabinet, conduit body, or other fitting. After that first 12-inch securing point, NM cable must be supported at intervals not exceeding 4.5 feet. This prevents the cable from sagging or being strained at the entry point.
Why the other choices are wrong
- A.6 inches applies to flexible conduit (FMC) securing requirements, not NM cable.
- B.8 inches is not a standard securing distance in the NEC for any common wiring method.
- D.18 inches would allow too much unsupported cable at the box entry, the code requires 12 inches.
Question 9: In habitable rooms of a dwelling unit, receptacles must be spaced so that no point along the floor line of any wall space is more than how many feet from a receptacle outlet?
- A.4 feet
- B.6 feet
- C.8 feet
- D.10 feet
Correct answer: B. 6 feet. NEC 210.52(A)(1) requires that receptacles in dwelling habitable rooms be spaced so that no point along the floor line of a wall space is more than 6 feet from a receptacle. This means receptacles must be placed every 12 feet or less (6 feet from either direction). The intent is to eliminate the need for extension cords.
Why the other choices are wrong
- A.4 feet would require receptacles every 8 feet, tighter than what the code requires.
- C.8 feet exceeds the code limit and would allow wall sections with no receptacle within reach.
- D.10 feet is well beyond the code maximum and would allow long stretches of wall without a receptacle.
Question 10: A service is supplied by 2/0 AWG copper service-entrance conductors. Per NEC Table 250.66, what is the minimum size copper grounding electrode conductor (GEC) required?
- A.6 AWG copper
- B.4 AWG copper
- C.2 AWG copper
- D.1/0 AWG copper
Correct answer: B. 4 AWG copper. NEC Table 250.66 requires a minimum 4 AWG copper GEC when the service-entrance conductors are 2/0 AWG copper. This table is based on the size of the service-entrance conductors, not the service rating. Knowing Table 250.66 by heart will save time on the exam, it covers the most common residential service sizes.
Why the other choices are wrong
- A.6 AWG GEC is only acceptable for service conductors up to 1/0 AWG copper, too small for 2/0 AWG service conductors.
- C.2 AWG copper GEC is required for service-entrance conductors over 3/0 up through 350 kcmil (for example 4/0 AWG), not 2/0.
- D.1/0 AWG GEC is required only when service conductors exceed 350 kcmil copper.
Question 11: For a Design B motor, what is the maximum rating of a dual-element (time-delay) fuse used for branch-circuit short-circuit and ground-fault protection, expressed as a percentage of motor full-load current?
- A.125%
- B.150%
- C.175%
- D.225%
Correct answer: C. 175%. NEC Table 430.52 sets the maximum fuse rating for motor branch-circuit protection. For a dual-element (time-delay) fuse protecting a Design B motor, the maximum is 175% of the motor's full-load current. Time-delay fuses are preferred for motor circuits because they tolerate the high inrush current at startup without nuisance tripping.
Why the other choices are wrong
- A.125% is used for ampacity sizing of motor branch-circuit conductors, not for overcurrent device ratings.
- B.150% is not a listed multiplier in Table 430.52 for dual-element fuses.
- D.225% is not a listed value in Table 430.52. A non-time-delay fuse is permitted up to 300% and an inverse time breaker up to 250%, but the dual-element time-delay fuse maximum is 175%.
Question 12: When 4 to 6 current-carrying conductors are installed in the same raceway or cable, the ampacity from Table 310.16 must be reduced by applying what adjustment factor?
- A.70%
- B.80%
- C.85%
- D.90%
Correct answer: B. 80%. NEC 310.15(C)(1) and Table 310.15(C)(1) require an 80% adjustment factor when 4 to 6 current-carrying conductors share the same raceway or cable. For example, a 12 AWG THWN conductor rated 25A in the 75°C column of Table 310.16 would be adjusted to 20A (25A × 0.80). Always check conductor count before sizing, bundling conductors traps heat and reduces safe ampacity.
Why the other choices are wrong
- A.70% applies when 7 to 9 current-carrying conductors share the same raceway or cable.
- C.85% is not a listed adjustment factor in Table 310.15(C)(1) for any conductor count range.
- D.90% applies when there are only 3 or fewer current-carrying conductors, no derating is needed.
Question 13: What is the minimum working clearance depth required in front of electrical equipment operating at 120-240 volts to ground under Condition 1 per NEC 110.26(A)(1)?
- A.2 feet
- B.2.5 feet
- C.3 feet
- D.4 feet
Correct answer: C. 3 feet. NEC 110.26(A)(1), Condition 1 requires a minimum working space depth of 3 feet in front of electrical equipment operating up to 150 volts to ground. For equipment from 151V to 600V to ground, the minimum varies by condition. The 3-foot rule for low-voltage panels is one of the most frequently tested working clearance requirements.
Why the other choices are wrong
- A.2 feet is insufficient for any voltage level under 110.26(A)(1).
- B.2.5 feet does not meet the minimum 3-foot requirement for Condition 1.
- D.4 feet applies to higher voltage equipment or specific Condition 3 installations.
Question 14: Which of the following is NOT a standard ampere rating for fuses and inverse time circuit breakers listed in NEC 240.6(A)?
- A.70 amperes
- B.75 amperes
- C.80 amperes
- D.90 amperes
Correct answer: B. 75 amperes. NEC 240.6(A) lists the standard ampere ratings for fuses and inverse time circuit breakers. The sequence runs 70, 80, 90, 100 in this range, so 75 amperes is not a standard listed rating. When a calculated load falls between standard sizes, 240.4(B) lets you round up to the next standard size, provided the conductor is protected at or below its ampacity. Knowing which sizes are standard helps you spot wrong answers quickly on the exam.
Why the other choices are wrong
- A.70 amperes IS a standard rating listed in NEC 240.6(A).
- C.80 amperes IS a standard rating listed in NEC 240.6(A).
- D.90 amperes IS a standard rating listed in NEC 240.6(A).
Question 15: When connecting conductors to terminals of equipment, the temperature rating of the conductor at the termination is limited to what value per NEC 110.14(C)?
- A.The temperature rating of the conductor insulation
- B.75°C regardless of conductor rating
- C.The temperature rating of the lowest-rated component in the connection
- D.90°C if the conductor is rated 90°C
Correct answer: C. The temperature rating of the lowest-rated component in the connection. NEC 110.14(C) establishes that the temperature rating at a termination is limited by the lowest-rated component in the connection, whether that is the conductor, the terminal, or the device. This is why 90°C-rated THHN conductors are almost always derated to 75°C for ampacity purposes: most terminals and equipment are only rated 75°C. Always match your ampacity table column to the lowest temperature rating in the circuit.
Why the other choices are wrong
- A.The conductor insulation rating doesn't govern alone, the terminal rating can be lower, and the lower one controls.
- B.75°C is commonly used in practice, but it's because most terminals are 75°C-rated, the code rule is based on the lowest component, not a fixed 75°C rule.
- D.Using 90°C ampacity is only permitted when both the conductor AND the connected equipment are rated 90°C, which is rarely the case.
These 15 explanations are just a sample
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About This Free Electrician Practice Test
All 15 questions are written around NEC 2023, which is the edition most states are testing on for journeyman and master electrician licensing exams in 2025 and 2026. Each question targets a specific NEC article, section, or table that appears frequently in state licensing exams. Topics include fundamental calculations like the 125% continuous load rule and conduit fill limits, as well as commonly missed rules like GEC sizing from Table 250.66 and termination temperature restrictions from NEC 110.14.
This test is designed as a quick diagnostic, 15 questions takes most people 10 to 15 minutes. A score of 70% or better (11 out of 15) suggests you are in the range where focused study on your weak areas can push you to a passing score on the real exam. Below 70% usually means there are foundational code concepts that need more review before test day.