10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
These 10 free 2C questions are organized by exam domain, so you can see how each part of the Electrical Plan Review (2C) blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: Cabinets, Panelboards, Switchboards, Boxes, and Conduit Bodies
Question 1
A renovation drawing evaluated under the 2020 NEC routes an unrelated feeder through a panelboard enclosure and makes splices in its wiring space. At the most crowded cross section, conductors occupy 36% of the wiring space; conductors and splices together occupy 68%. The equipment instructions permit the arrangement, and required bending space is maintained. The enclosure label identifies only the panelboard's own disconnect. Which single change is needed to make this routing detail compliant?
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Correct answer: D - Add an enclosure warning label identifying the closest disconnect for the feed-through conductors.
Domain 2: Calculations of Load
Question 2
A new dwelling's entire load is supplied by one 200 A, 120/240 V, three-wire service. Its designer elects the optional calculation in 220.82 of the 2020 NEC. The range is rated 11.5 kW and the electric dryer 4.6 kW. Before applying the optional method's general-load demand factor, which pair of appliance loads belongs in the subtotal?
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Correct answer: B - 11.5 kW for the range and 4.6 kW for the dryer
Question 3
An office-building floor has 24,000 square feet and 90 duplex receptacles, each on its own yoke. All are general-use receptacles; none serves a separately calculated dedicated load. For the feeder calculation under the 2020 NEC, what receptacle load must be carried forward after applying the permitted demand factor and the office-area minimum?
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Correct answer: D - 24,000 VA
Domain 3: Calculations of Wire Size
Question 4
A 480 V branch circuit supplies a fixed 70 A nonmotor load for eight hours at a time. It uses a 90 A breaker and 4 AWG copper THHN conductors connected directly to equipment with 75°C terminals. NEC 2020 Table 310.16 gives 85 A at 75°C and 95 A at 90°C; ambient correction reduces the 90°C value to 86.45 A. The assembly is not listed for continuous operation at 100% of its rating. Which condition controls the decision to accept or reject these conductors?
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Correct answer: A - Reject it because the uncorrected 75°C ampacity is less than 125% of the continuous load.
Domain 7: Motors other than Dwellings
Question 5
During a pump replacement, a motor with lower nameplate current is proposed at the same 15 hp, 460 V, three-phase, 1,760 rpm ratings. Both motors are ordinary, single-speed, normal-torque models started across the line. NEC 2020 Table 430.250 gives 21 A for either motor. Which current bases belong in the revised conductor and protection specifications?
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Correct answer: B - Use table current for conductors and branch short-circuit protection; use replacement nameplate current for separate overload protection.
Domain 8: Service Equipment and Conductors on the Supply Side of the Service
Question 6
The short-circuit study for a 480 V commercial service reports 28 kA rms symmetrical available fault current at the proposed switchboard. The switchboard's marked short-circuit current rating is 22 kA; its main breaker has a 65 kA interrupting rating at 480 V. No higher assembly or combination rating is established. Under the 2020 NEC, what keeps this submittal from being acceptable?
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Correct answer: B - The switchboard's short-circuit rating remains below the available fault current.
Domain 9: Special Installations or Constructions
Question 7
Equipotential bonding and 30 mA ground-fault protection of equipment are shown for a new permanently installed pool pump. The pump is hardwired to a 50 A, three-phase branch circuit supplied from a 208Y/120 V system. There is no Class A GFCI. Under the 2020 NEC, the plan reviewer should:
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Correct answer: C - Provide Class A GFCI protection for the motor outlet.
Domain 10: Special Occupancies
Question 8
Normal operation of a solvent process produces ignitable concentrations of Group D vapor where an electrical component will be installed. The solvent's autoignition temperature is 225°C. The drawings follow the NEC 2020 Class/Division system, and the ambient temperature is within every candidate product's listed range. Which marking matches both the hazardous-location classification and the temperature conditions?
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Correct answer: A - Class I, Division 1, Group D; T3, 200°C maximum surface temperature.
Question 9
During a controlled test of an operating-room isolated power system, a test device raises the line isolation monitor's indicated total hazard current to 6.4 mA at nominal voltage. The monitor uses a 5 mA total-hazard-current alarm design. There is no overload or line-to-line fault. Which observed response demonstrates the intended NEC 2020 line isolation monitor function?
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Correct answer: C - The red indicator and audible warning operate while power remains available.
Domain 12: Wiring Methods
Question 10
'The solvent-welded joints and sealed ends will keep these conductors dry,' says the designer. The site plan specifies conductors marked only THHN, with no wet-location listing, in an underground Schedule 80 PVC raceway. Under the 2020 NEC, what revision, if any, does this conductor specification need?
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Correct answer: D - Specify wet-location-rated conductors because the underground raceway interior is a wet location.