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Tap an answer to see if you are right, and why. 20 questions across 11 topics, mostly Wiring methods (2).
Wiring methods1 of 20
The answer
Answer: C. EMT is lightweight, easy to bend, and approved for exposed work in commercial buildings. NM-B is limited to dry, concealed locations in residential wood-frame construction.
Source: NEC 358.10 — Installation: Wiring Methods: EMT Use
Grounding and bonding2 of 20
The answer
Answer: C. Table 250.66 sizes the grounding electrode conductor from the largest ungrounded service conductor. A 200-amp residential service typically uses 2/0 or 3/0 AWG copper, and for service conductors of 2/0 through 3/0 AWG the table requires a 4 AWG copper GEC. 6 AWG is only permitted for 1/0 AWG or smaller service conductors.
Source: NEC Table 250.66 — Grounding: Grounding Electrode Conductor Sizing
Boxes and conduit3 of 20
The answer
Answer: C. Under NEC 314.16(B), the six 12 AWG conductors count 6 × 2.25 = 13.5 in³, the internal clamps count once at the largest conductor (2.25 in³), and the receptacle's yoke counts twice (4.5 in³). A conductor no part of which leaves the box, such as a pigtail, is not counted. Total: 20.25 in³. Counting the pigtails gives the wrong 24.75 in³.
Source: NEC 314.16(B) — Installation: Boxes and Conduit Bodies: Box Fill Calculations
Conductor sizing4 of 20
The answer
Answer: A. Table 310.16: 8 AWG copper is rated 50 amps at 75°C, which is sufficient for a 40-amp circuit; 10 AWG (35 A at 75°C) is too small. 6 AWG would work but is not the minimum. The 60°C column (40 A for 8 AWG) only governs where terminations are not rated 75°C.
Source: NEC 310.16 — Conductors: Allowable Ampacities
Overcurrent protection5 of 20
The answer
Answer: C. Manufacturer listing requirements take precedence. The NEC requires that equipment be installed per its listing, which includes the specified overcurrent protection rating.
Source: NEC 110.3(B) — Installation: Equipment Listing: Manufacturer Instructions
Motors6 of 20
The answer
Answer: A. NEC 430.22 requires branch-circuit conductors for a single motor to have an ampacity of at least 125% of the motor full-load current from Table 430.248: 28 × 1.25 = 35 amps. 10 AWG copper THWN is rated 35 amps at 75°C in Table 310.16, so 10 AWG is the minimum; 8 AWG (50 A) is larger than required.
Source: NEC 430.22 — Motors: Branch Circuit Conductors
Load calculations7 of 20
The answer
Answer: C. Table 220.55, Column C: for one household range rated not over 12 kW, the standard-method demand load is 8 kW. The 12 kW nameplate is not used directly, and Note 1 (5% per kW over 12 kW) does not apply to a 12 kW range.
Source: NEC 220.55 — Load Calculations: Household Electric Ranges
Service sizing8 of 20
The answer
Answer: C. Receptacles: 120 × 180 VA = 21,600 VA; Table 220.44 allows the first 10 kVA at 100% and the remainder at 50%, so 10,000 + 5,800 = 15,800 VA. Lighting: 40 × 150 VA = 6,000 VA at 100%. Air conditioning: 7,000 VA at 100%. Total = 15,800 + 6,000 + 7,000 = 28,800 VA, or 28.8 kVA.
Source: NEC 220.44 — Receptacle Loads: Nondwelling Demand Factors
Voltage drop9 of 20
The answer
Answer: D. Single-phase voltage drop = 2 × K × I × D ÷ CM, with K = 12.9 for copper, I = 80 A, D = 300 ft and 2/0 AWG = 133,100 circular mils: 2 × 12.9 × 80 × 300 ÷ 133,100 ≈ 4.65 volts. 4.65 ÷ 240 = 1.9%, within the 3% recommended for feeders in the informational note to 215.2.
Source: NEC 90.0(A) — Installation: Purpose: Adequacy of Wiring
Safety10 of 20
The answer
Answer: B. NFPA 70E requires lockout/tagout of all energy sources before working on energized or potentially energized equipment. A non-contact tester alone is insufficient and rubber gloves are PPE, not a substitute for LOTO.
Source: NFPA 70E 120.5 — Safety: Establishing an Electrically Safe Work Condition
Maintenance11 of 20
The answer
Answer: D. A megohmmeter tests insulation resistance and can detect degraded insulation that causes intermittent ground faults. A clamp meter measures current but cannot identify insulation breakdown.
Source: NEC 110.5 — Maintenance: Conductors: General
Wiring methods12 of 20
The answer
Answer: C. NM-B cable cannot be installed in wet locations or below grade. A concrete slab-on-grade is a wet location where NM cable is not permitted without additional protection.
Source: NEC 334.12(A) — Wiring Methods: Uses Permitted: Wet Locations
Grounding and bonding13 of 20
The answer
Answer: D. The bonding jumper to a metallic water pipe must be connected within 5 feet of the point of entrance into the building to ensure an effective ground-fault current path.
Source: NEC 250.68(C)(1) — Grounding Electrode Conductor Connections: Metal Water Pipe
Boxes and conduit14 of 20
The answer
Answer: D. Per NEC Chapter 9 Table 1, 3/4-inch EMT at 40% fill has a cross-sectional area of 0.213 in². Four 10 AWG THHN conductors at 0.0211 in² each equals 0.0844 in², which is well within the allowable fill.
Source: NEC Chapter 9, Table 1 — Installation: Conduit Fill
Conductor sizing15 of 20
The answer
Answer: D. Table 310.16: 3/0 AWG copper at 75°C is rated 200 amps, so it is the smallest size that carries a 200-amp feeder; 2/0 AWG is only 175 amps. (310.12 allows 2/0 copper only for a 200-amp dwelling service or feeder that supplies the entire dwelling load, which this subpanel feeder does not.)
Source: NEC 310.16 — Conductors: Allowable Ampacities
Overcurrent protection16 of 20
The answer
Answer: D. The disconnect can be rated higher than the overcurrent device. The fuse size must match the equipment's listed maximum, not the disconnect's rating, per the equipment listing.
Source: NEC 240.60(A) — Overcurrent Protection: Enclosed Fuses
Motors17 of 20
The answer
Answer: D. Table 430.52 allows an inverse-time breaker of up to 250% of the motor full-load current: 28 × 2.5 = 70 amps, which is a standard size in 240.6(A). Where 250% does not land on a standard size, 430.52(C)(1) Exception 1 permits the next standard size up.
Source: NEC 430.52 — Motors: Branch-Circuit Short-Circuit Protection
Load calculations18 of 20
The answer
Answer: D. Four circuits × 120 V × 20 A = 9,600 VA. Under the optional method in 220.82(B), the general loads are taken at 100% for the first 10 kVA and 40% for the remainder. 9,600 VA is under 10 kVA, so the full 9,600 VA applies.
Source: NEC 220.82(B) — Optional Calculation: Dwelling Unit General Loads
Service sizing19 of 20
The answer
Answer: A. Per NEC 220.54, two dryers are calculated at 5.0 kW each using Table 220.54 Column C for two or more dryers, totaling 10.0 kW.
Source: NEC 220.54 — Load Calculations: Electric Dryers
Voltage drop20 of 20
The answer
Answer: A. Voltage drop = 2 × 12.9 × 20 × 300 / 16,510 = 9.36 volts, approximately 4.0% of 240V. This exceeds the recommended 3% for branch circuits and may require upsizing conductors.
Source: NEC 90.0(A) — Installation: Purpose: Voltage Drop Considerations
The official California General Electrician knowledge examination covers 100 multiple-choice questions with a passing threshold of 70%. Questions written from the CA DLSE General Electrician content outline and verified against NEC 2023. Every question on this page is original, with an explanation and a note citing its source.
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