Forty exam-style questions spanning all nine topic areas of the 2023
National Electrical Code® — each cross-verified, with the article
reference on every answer. No signup, no timer, no tricks. Grab your code book;
the real exam is open book, and so is this one.
Answer each question to see the explanation, then move on. Your
per-topic breakdown at the end tells you exactly what to study next.
Which NEC edition? These are general NEC 2023 practice questions, not matched to any particular licensing exam. Three different dates answer three different questions: NFPA issued the 2026 edition in August 2025 (Standards Council final minutes); Washington's installation rules adopt the 2023 edition until the 2026 edition replaces it on December 31, 2026 (WAC 296-46B-010); and Washington's electrical licensing exams are based on the 2020 NEC (PSI candidate bulletin). Check which edition your own exam and jurisdiction use.
Question 1 of 40
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Question 1 · Branch Circuits & Feeders · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A branch circuit supplies only a 24 A continuous load. No exception to the ordinary conductor-sizing rule applies, including the 100%-rated-assembly exception. Before ampacity correction or adjustment, what minimum ampacity does 210.19(A)(1) require for the ungrounded conductors?
NEC 2023 210.19(A)(1) — The ordinary calculation is 24 x 1.25 = 30 A. This is the pre-correction/adjustment requirement in 210.19(A)(1), not a completed conductor selection. The other applicable ampacity and termination requirements must also be satisfied.
Question 2 · Equipment for General Use · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
An existing receptacle is being replaced at a location where GFCI protection is now required by 210.8. What does 406.4(D) require of the replacement receptacle?
NEC 2023 406.4(D)(3) — 406.4(D)(3) requires that where a receptacle is replaced at a location that now requires GFCI protection, the replacement be provided with GFCI protection.
Question 3 · General Theory & Definitions · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A heating element with a resistance of 20 ohms is connected to a 120-volt source. Ignoring temperature effects, what current flows through the element?
Electrical theory - Ohm's law — By Ohm's law, I = E / R = 120 V / 20 ohms = 6 A. Choice D results from multiplying instead of dividing (120 x 20); the others come from using an incorrect resistance value.
Question 4 · Grounding & Bonding · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
The GEC for a large service connects solely to a concrete-encased (Ufer) electrode. What is the largest copper GEC size the Code requires you to run to that electrode?
NEC 2023 250.66(B) — Where the GEC connects only to a concrete-encased electrode, that portion need not be larger than 4 AWG copper. The 6 AWG allowance applies to rod/pipe/plate electrodes, not the concrete-encased electrode.
Question 5 · Overcurrent Protection · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Conductors with an allowable ampacity of 95 A protect a feeder that meets all conditions of the next-higher-standard-rating rule. What is the maximum standard overcurrent device rating permitted?
NEC 2023 240.4(B) — 95 A is not a standard rating and sits between 90 and 100; the next higher standard rating permitted under 240.4(B) is 100 A.
Question 6 · Services · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Overhead service conductors cross above a public street that is subject to truck traffic. What is the minimum required vertical clearance?
NEC 2023 230.24(B)(4) — 230.24(B)(4) requires 18 ft over public streets, alleys, roads, and areas subject to truck traffic. The 12 ft value is for residential property and driveways; 10 ft is the pedestrian-only value.
Question 7 · Special Equipment & Conditions · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
The equipotential bonding for a permanently installed pool must include the perimeter surfaces around the pool. Measured horizontally beyond the inside walls of the pool, how far do these bonded perimeter surfaces extend?
NEC 2023 680.26(B)(2) — 680.26(B)(2) defines the perimeter surface as extending 3 ft horizontally beyond the inside walls of the pool, and it must be part of the equipotential bonding. The other values do not match the Code dimension.
Question 8 · Special Occupancies · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
During a walkthrough of an aircraft hangar you find a floor-level maintenance pit dug beneath where aircraft sit so workers can reach the underside of the airframe. Which hazardous (classified) location designation applies inside that pit?
NEC 2023 513.3(A) — 513.3(A) classifies any pit or depression below the level of the hangar floor as Class I, Division 1, since heavier-than-air vapors collect in such low spaces.
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Using Annex C, Table C.1, how many 12 AWG THHN conductors (all the same size) are permitted in a 3/4 in. trade size EMT?
NEC 2023 Annex C, Table C.1 — Annex C, Table C.1 (EMT, THHN): 3/4 in. EMT holds 16 twelve-AWG conductors. The value 9 is for 1/2 in. EMT and 22 is the count for 14 AWG in 3/4 in. EMT.
Question 10 · Branch Circuits & Feeders · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
In a dwelling family room, general receptacle placement is governed by the rule that no point measured horizontally along the floor line of any wall space may be more than a stated distance from a receptacle outlet. What is that distance?
NEC 2023 210.52(A)(1) — 210.52(A)(1) sets the 1.8 m (6 ft) point-to-receptacle limit so a 1.8 m appliance cord reaches from either side. The 12 ft figure is the resulting maximum spacing between two outlets, not the distance from a point to a receptacle.
Question 11 · Equipment for General Use · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A wall-mounted general-use snap switch is being installed in a finished basement. Measured to the center of the grip of the operating handle in its highest position, what is the maximum height above the finished floor or working platform permitted?
NEC 2023 404.8(A) — 404.8(A) limits the center of the operating-handle grip, in its highest position, to a maximum of 6 ft 7 in (2.0 m) above the floor or working platform.
Question 12 · General Theory & Definitions · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
According to Article 90, what is the stated purpose of the National Electrical Code?
NEC 2023 90.2(A) and 90.2(B) — Article 90 states the Code's purpose as safeguarding people and property from electrical hazards. The same section makes clear the NEC is a safety document rather than a design guide or a how-to manual for people without electrical training, and 90.2(B) separately notes that meeting the Code does not by itself guarantee an efficient, convenient or expandable installation.
Question 13 · Grounding & Bonding · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A ground rod is being installed as the sole made electrode for a residence. What is the minimum length of rod that must be in contact with the soil?
NEC 2023 250.52(A)(5) and 250.53(G) — Rod-type electrodes must be at least 8 ft long and installed so at least 8 ft is in contact with the soil. The other lengths are plausible but incorrect values.
Question 14 · Overcurrent Protection · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
For 14 AWG copper, what overcurrent-rating ceiling is specified by the ordinary small-conductor rule in 240.4(D), with no permission under 240.4(E) or (G) being used?
NEC 2023 240.4(D) and 240.4(D)(4) — The specified small-conductor ceiling is 15 A for 14 AWG copper, found in 240.4(D)(4) in the 2023 edition. This is a ceiling under that rule; ampacity correction, adjustment or another applicable requirement can still require a lower protective rating.
Question 15 · Services · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A service disconnecting means for a dwelling may be installed in each of the following locations EXCEPT which one?
NEC 2023 230.70(A)(2) — 230.70(A)(2) prohibits installing the service disconnecting means in a bathroom. The other listed locations are permissible provided the disconnect is readily accessible.
Question 16 · Special Equipment & Conditions · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
For a permanently installed outdoor pool, a copper wire conductor is selected for the equipotential connection between parts required to be bonded by 680.26(B). Among the following choices, what is the minimum conductor size and construction for that wire method?
NEC 2023 680.26(B) — The minimum for the stated wire method is 8 AWG solid copper. Stranded 8 AWG does not meet the stated construction requirement, and 10 AWG solid is too small. The 6 AWG solid choice is larger than required, so it is not the minimum answer; it is not prohibited merely for being larger.
Question 17 · Special Occupancies · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A processing room contains suspended metal powder that can ignite when airborne. Under the NEC classification scheme, which hazardous (classified) location Class is defined by the presence of this hazard?
NEC 2023 500.5(C) — Class II locations are those made hazardous by the presence of combustible dust, per 500.5(C). Class I covers flammable gases/vapors and Class III covers ignitible fibers/flyings; there is no Class IV.
Question 18 · Wiring Methods & Materials · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Type NM cable installed on the surface of framing members must be secured within what distance of each outlet box or cabinet, and supported at what maximum interval along the run?
NEC 2023 334.30 — 334.30 requires Type NM cable to be secured within 12 in. of every box/cabinet and supported at intervals not exceeding 4-1/2 ft. The 6 ft interval belongs to Type MC (330.30).
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A feeder supplies 200 A noncontinuously and 100 A continuously. For its ungrounded conductors, no exception to 215.2(A)(1) applies, including the 100%-rated-assembly exception. With suitable 75 C terminations and no ampacity correction or adjustment factors, what minimum conductor ampacity is required?
NEC 2023 215.2(A)(1) — The ordinary-rule result is 200 + (100 x 1.25) = 325 A. Using 300 A omits the continuous-load factor; using 375 A incorrectly applies that factor to the full load.
Question 20 · Equipment for General Use · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A recessed luminaire that is NOT identified for contact with insulation (not Type IC) is installed in an insulated ceiling. What minimum spacing must be maintained between thermal insulation and the luminaire enclosure, wiring compartment, and ballast?
NEC 2023 410.116(B) — 410.116(B) requires that thermal insulation not be installed within 3 in of a recessed luminaire enclosure, wiring compartment, or ballast unless the luminaire is identified for insulation contact (Type IC).
Question 21 · General Theory & Definitions · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A 1200-ampere switchboard containing overcurrent devices is 8 ft wide and requires examination while energized. Neither single-entrance exception in 110.26(C)(2) applies. Which entrance arrangement is required for its working space?
NEC 2023 110.26(C)(1), (C)(2), and (C)(3) — Both ends need an entrance at least 24 in. wide and 6.5 ft high under 110.26(C)(2). This switchboard meets the rating, width and equipment conditions, and the question excludes the single-entrance exceptions. The 800 A personnel-door provision in (C)(3) is a different requirement.
Question 22 · Grounding & Bonding · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A service uses two parallel sets of 600 kcmil copper conductors per phase, connected to a metal water pipe electrode. What is the minimum size copper grounding electrode conductor?
NEC 2023 Table 250.66 — For parallel conductors, Table 250.66 is applied to the equivalent area: 2 x 600 = 1200 kcmil per phase, which is over 1100 kcmil. That range requires a 3/0 AWG copper GEC. Sizing from a single 600 kcmil conductor is the common error.
Question 23 · Overcurrent Protection · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A branch circuit supplying several receptacles for cord-and-plug-connected portable loads uses conductors with an allowable ampacity of 34 A. What is the maximum standard overcurrent device rating permitted?
NEC 2023 240.4(B) — The next-higher-standard allowance is not permitted because condition (1) of 240.4(B) excludes branch circuits supplying more than one receptacle for cord-and-plug portable loads. So you cannot round up to 35 A; the device must not exceed the next lower standard rating, 30 A.
Question 24 · Services · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A service supplies a 100 A noncontinuous load and a 120 A continuous load. Using 230.42(A)(1), what is the minimum required ampacity of the service-entrance conductors?
NEC 2023 230.42(A)(1) — 230.42(A)(1) requires the sum of the noncontinuous load plus 125 percent of the continuous load: 100 + (1.25 x 120) = 100 + 150 = 250 A.
Question 25 · Special Equipment & Conditions · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A rooftop PV installation on a building uses the voltage-limited compliance option in 690.12(B)(2)(2) for controlled conductors inside the array boundary. What maximum voltage must be reached within 30 seconds after rapid shutdown starts?
NEC 2023 690.12(B)(2)(2) — This option limits the relevant voltage inside the array boundary to 80 V within 30 seconds. The limit applies between conductors and between a conductor and ground. A listed PV hazard control system is an alternative compliance route; the 80 V answer should not be stated as the only route.
Question 26 · Special Occupancies · difficult
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A parked aircraft in a hangar has integral fuel tanks and power plants. Measured horizontally outward from the aircraft power plants and fuel tanks, the surrounding air is classified as Class I, Division 2. What horizontal distance does this vicinity-of-aircraft classification extend?
NEC 2023 513.3(C) — 513.3(C) classifies the area within 5 ft horizontally of aircraft power plants or aircraft fuel tanks as Class I, Division 2 (or Zone 2), extending upward from that area as specified.
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
In a junction box containing 4 AWG and larger conductors, the minimum length for a straight pull must be at least how many times the trade diameter of the largest raceway?
NEC 2023 314.28(A)(1) — 314.28(A)(1): for straight pulls the box length must be at least 8 times the trade diameter of the largest raceway. The 6-times factor applies to angle and U pulls under 314.28(A)(2).
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A feeder supplies 160 A continuously and 40 A noncontinuously. For its ungrounded conductors, no exception to 215.2(A)(1) applies, including the 100%-rated-assembly exception. Ignoring ampacity correction and adjustment factors, what minimum conductor ampacity does the ordinary rule require?
NEC 2023 215.2(A)(1) — Use 40 + (160 x 1.25) = 240 A. The 200 A choice simply adds the two loads without the required ordinary-rule continuous-load factor. This question excludes the exceptions and asks for the load-based ampacity calculation.
Question 29 · Equipment for General Use · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A new panelboard uses the ordinary bus arrangement for a three-phase, four-wire delta system with one winding midpoint grounded. No alternate bus arrangement or metering exception applies. If the high leg is identified using the color specified in 110.15, which phase and color combination is correct?
NEC 2023 408.3(E)(1) and 110.15 — Phase B is the high-leg position for the stated arrangement. Section 110.15 specifies orange when that color method is used, while also allowing other effective identification. The question excludes alternate bus arrangements and asks specifically for the named color method.
Question 30 · General Theory & Definitions · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A purely resistive load draws 10 A RMS from a 120 V RMS single-phase ac source. The power factor is 1. What average real power does the load consume?
Electrical theory: resistive ac load, average power using RMS voltage and current; OpenStax University Physics Volume 2, section 15.4, Equation 15.13 — For this resistive load, average power is 120 x 10 = 1200 W. Dividing the displayed numbers gives 12 and adding them gives 130, but neither calculates power. The 144 W choice is simply an incorrect result; squaring the 10 A current would produce 100, not 144.
Question 31 · Grounding & Bonding · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Two rod electrodes are installed to form a grounding electrode system. What is the minimum spacing required between them?
NEC 2023 250.53(A)(3) — Where more than one rod, pipe, or plate electrode is used, each must be at least 6 ft apart. The 8 ft distractor mirrors the rod length, a common source of confusion.
Question 32 · Overcurrent Protection · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A set of feeder conductors has an allowable ampacity of exactly 100 A. What is the maximum standard overcurrent device rating permitted to protect them?
NEC 2023 240.4(B) — The next-higher-standard allowance applies only when the conductor ampacity does not correspond to a standard rating. Because 100 A is itself a standard rating, you cannot round up; the maximum is 100 A.
Question 33 · Services · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Open service conductors run alongside a wall must maintain a minimum clearance from a window designed to be opened. What is that clearance?
NEC 2023 230.9(A) — 230.9(A) requires a clearance of not less than 3 ft from windows that open, doors, porches, balconies, and similar locations. Conductors run above the top level of a window are exempt from this clearance.
Question 34 · Special Equipment & Conditions · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
A sign has an electronic controller outside the sign enclosure. Its disconnect is being located under the ordinary controller-location route in 600.6(A)(3), without using the out-of-sight exception. All other switching, lockability, accessibility and remote-location requirements are satisfied. Which choice meets this location condition?
NEC 2023 600.6(A)(3) and (A)(4); 110.25 — The ordinary controller route places the disconnect in sight of the controller or inside the controller enclosure. Its other conditions include disconnecting the sign and controller from all ungrounded supply conductors, preventing independent energization of a pole, and lockability under 110.25. A service-equipment or same-floor location alone does not establish the required relationship. Remote disconnect locations also have the access and identification requirements in 600.6(A)(4).
Question 35 · Special Occupancies · moderate
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Across the general floor area of an aircraft hangar (not near the aircraft itself), a Class I, Division 2 classification applies from the floor upward to a fixed height. What is that height above the floor?
NEC 2023 513.3(B) — 513.3(B) classifies the entire hangar floor area, including adjacent and communicating areas, as Class I, Division 2 up to a level 18 in. above the floor.
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
In a box-fill calculation, how is a single duplex receptacle (a device on a yoke) counted, and on what conductor size is that allowance based?
NEC 2023 314.16(B)(4) — 314.16(B)(4): each yoke or strap containing one or more devices is counted as two volume allowances based on the largest conductor connected to the device.
Question 37 · Branch Circuits & Feeders · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
What is the minimum number of 20-ampere small-appliance branch circuits required to supply the receptacle outlets in a dwelling kitchen, pantry, breakfast room, and dining room?
NEC 2023 210.11(C)(1) — 210.11(C)(1) requires at least two 20 A small-appliance branch circuits to serve those areas; these are in addition to the required laundry and bathroom circuits.
Question 38 · Equipment for General Use · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
In a new dwelling unit, the 15- and 20-ampere, 125-volt nonlocking receptacles installed in the required locations must be what type?
NEC 2023 406.12 — 406.12 requires all 15- and 20-ampere, 125- and 250-volt nonlocking receptacles in the listed dwelling-unit areas to be listed tamper-resistant.
Question 39 · Wiring Methods & Materials · easy
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Electrical metallic tubing (EMT) must be securely fastened within what distance of each outlet box, junction box, or fitting, and supported at what maximum interval?
NEC 2023 358.30(A) — 358.30(A) requires EMT to be fastened within 3 ft of each termination and supported at intervals not exceeding 10 ft.
NEC 2023 · General practice — jurisdiction-specific amendments not evaluated.
Conductor ampacity adjustment (derating) factors for a metal wireway are required only when the number of current-carrying conductors at any cross-section exceeds what value?
NEC 2023 376.22(B) — 376.22(B): the adjustment factors of 310.15(C)(1) apply only where the number of current-carrying conductors in the wireway exceeds 30 (the neutral rules of 310.15(E) still apply).
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