NASCLA Accredited Professional Electrical Contractor Exam — Questions and Answers

Question 1: When installing EMT in a concrete slab, what NEC requirement applies to the minimum concrete cover?

EMT requires no cover in concrete
½ inch minimum cover
No minimum — EMT is not permitted in concrete
2 inch minimum cover (Correct answer)

Correct answer: 2 inch minimum cover

Per NEC 358.10(B) and 300.6(D), EMT embedded in concrete must have at least 2 inches of concrete cover unless listed for less.

Question 2: What is the role of a lighting circuit in electrical design?

To increase the circuit's voltage.
To regulate energy consumption.
To supply electricity to lighting fixtures while being properly protected. (Correct answer)
To control power for appliances.

Correct answer: To supply electricity to lighting fixtures while being properly protected.

A lighting circuit is specifically designed to provide electrical power to various lighting fixtures within a building. Its role is to ensure that these fixtures receive the correct voltage and current to operate effectively. Crucially, it must also be properly protected by circuit breakers or fuses to prevent overloads and short circuits, thereby ensuring safety and preventing damage to the wiring and fixtures.

Question 3: How often should electrical inspections be performed in residential areas?

Only when the system fails.
Every month.
After construction or major electrical work, or as required by code. (Correct answer)
Every year.

Correct answer: After construction or major electrical work, or as required by code.

Electrical inspections in residential areas should be performed after construction or major electrical work, or as specifically required by local codes. These inspections ensure that all electrical installations comply with safety standards and local regulations. Regular inspections are not typically monthly or yearly unless mandated by specific local ordinances or for commercial properties.

Question 4: Slip in an induction motor is defined as the difference between:

Synchronous speed and rotor speed (Correct answer)
Full-load current and no-load current
Line frequency and motor frequency
Applied voltage and induced voltage

Correct answer: Synchronous speed and rotor speed

Slip = (Ns - Nr) / Ns × 100%, representing the rotor's lag behind the rotating magnetic field.

Question 5: Which OSHA recordkeeping form is used to log work-related injuries and illnesses?

OSHA Form 101
OSHA Form 29
OSHA Form 1910
OSHA Form 300 (Correct answer)

Correct answer: OSHA Form 300

The OSHA 300 Log is the standard form employers use to record qualifying work-related injuries and illnesses throughout the year.

Question 6: Which wiring method is specifically listed for use in ducts, plenums, or other air-handling spaces without restriction?

Type AC cable
EMT with THHN conductors (Correct answer)
Type MC cable
Electrical nonmetallic tubing (ENT)

Correct answer: EMT with THHN conductors

EMT with THHN conductors is permitted in environmental air spaces; Type MC, AC, and ENT have restrictions under NEC 300.22.

Question 7: A dry-type transformer with an 80°C rise rating is installed in a room with a 40°C ambient temperature. What is the maximum operating winding temperature?

80°C
120°C (Correct answer)
40°C
160°C

Correct answer: 120°C

Maximum winding temperature equals ambient temperature plus temperature rise: 40°C + 80°C = 120°C, which must remain within the insulation class rating.

Question 8: Which factor most directly affects the labor productivity rate used in an electrical estimate?

The project location and working conditions (Correct answer)
The owner's payment terms
The type of bid bond required
The number of competing bidders

Correct answer: The project location and working conditions

Project location and working conditions—such as height, congestion, climate, and access—directly affect how efficiently electricians can install materials.

Question 9: In a place of assembly under NEC Article 518, which wiring method is specifically permitted in areas where the building is of fire-rated construction?

Type AC cable only in fire-rated walls
PVC conduit throughout
Type NM cable in any area
MI cable and metal-enclosed wiring systems (Correct answer)

Correct answer: MI cable and metal-enclosed wiring systems

NEC 518.4(A) requires metal-enclosed wiring methods such as MI cable, metal raceways, or metal-clad cable in fire-rated construction within places of assembly.

Question 10: In a series circuit, if one resistor increases in value, the total current will:

Decrease (Correct answer)
Double
Remain the same
Increase

Correct answer: Decrease

Higher resistance in a series circuit increases total resistance, reducing current per Ohm's Law.

Question 11: Which agency oversees and enforces electrical code compliance in the U.S.?

The Occupational Safety and Health Administration (OSHA). (Correct answer)
The U.S. Department of Energy.
The Federal Electrical Commission.
The National Fire Protection Association (NFPA).

Correct answer: The Occupational Safety and Health Administration (OSHA).

In the U.S., the Occupational Safety and Health Administration (OSHA) is the primary agency responsible for overseeing and enforcing electrical code compliance, particularly in workplaces. While the National Fire Protection Association (NFPA) develops the National Electrical Code (NEC), OSHA ensures that employers adhere to these standards to provide a safe working environment and prevent electrical hazards.

Question 12: OSHA's Hazard Communication Standard (29 CFR 1910.1200) requires Safety Data Sheets (SDS) to follow which format?

16-section GHS format (Correct answer)
12-section ANSI format
NFPA 704 diamond sections
8-section EPA format

Correct answer: 16-section GHS format

OSHA aligned its HazCom standard with the Globally Harmonized System (GHS), requiring a standardized 16-section SDS.

Question 13: What type of grounding electrode is NOT permitted to be used as the sole grounding electrode under NEC 250.52?

A single driven rod with resistance above 25 ohms (Correct answer)
Metal underground water pipe
Ground ring
Concrete-encased electrode

Correct answer: A single driven rod with resistance above 25 ohms

A single rod electrode with a measured resistance above 25 ohms must be supplemented with an additional electrode per NEC 250.56.

Question 14: Per NEC 450.21(A), a dry-type transformer rated 112.5 kVA or less may be installed indoors without a transformer vault if it is:

Only installed in a locked electrical room
Installed only on the lowest floor of the building
Placed in a listed enclosure only
Separated from combustible material by at least 12 inches or by a fire-resistant heat-insulating barrier (Correct answer)

Correct answer: Separated from combustible material by at least 12 inches or by a fire-resistant heat-insulating barrier

NEC 450.21(A) permits dry-type transformers 112.5 kVA or less to be installed indoors if separated from combustible materials by at least 300 mm (12 in.) or by a fire-resistant, heat-insulating barrier.

Question 15: In a typical commercial distribution system, primary distribution feeders in urban areas operate at what voltage range?

120/240V
4,160V to 15,000V (Correct answer)
115,000V to 345,000V
480V

Correct answer: 4,160V to 15,000V

Urban primary distribution feeders typically operate at medium voltages between 4,160V and 15,000V (commonly 4.16 kV, 12.47 kV, or 13.2 kV) before being stepped down to utilization voltage at the service point.

Question 16: A 480V, 3-phase balanced load consumes 50 kW at 0.8 PF lagging. What is the line current?

60.1 A
86.6 A
75.1 A (Correct answer)
43.4 A

Correct answer: 75.1 A

I = P / (√3 × VL × PF) = 50,000 / (1.732 × 480 × 0.8) ≈ 75.1 A.

Question 17: In a parallel circuit, which quantity remains the same across all branches?

Current
Resistance
Voltage (Correct answer)
Power

Correct answer: Voltage

Voltage is identical across all branches in a parallel circuit.

Question 18: Which type of estimate is typically used during early project design to determine project feasibility?

Conceptual or order-of-magnitude estimate (Correct answer)
Change order estimate
Definitive estimate
Bid estimate

Correct answer: Conceptual or order-of-magnitude estimate

A conceptual or order-of-magnitude estimate uses historical cost data and square footage costs to assess project feasibility before detailed design.

Question 19: What is the main purpose of electrical codes in residential areas?

To restrict the number of outlets and devices.
To ensure that electrical systems are aesthetically pleasing.
To ensure electrical systems are safe, reliable, and code-compliant. (Correct answer)
To minimize the cost of installation.

Correct answer: To ensure electrical systems are safe, reliable, and code-compliant.

The main purpose of electrical codes in residential areas is to ensure that electrical systems are safe, reliable, and compliant with established standards. These codes specify requirements for wiring, outlets, circuit protection, and grounding to prevent hazards such as electrical fires and shocks. Adherence protects residents and their property from electrical dangers.

Question 20: Which of the following would be classified as a direct cost in an electrical contracting estimate?

Wages for an electrician installing fixtures on the specific project (Correct answer)
The salary of the company's bookkeeper
Annual subscription fees for estimating software
Rent for the main office and warehouse

Correct answer: Wages for an electrician installing fixtures on the specific project

Direct costs are expenses that can be specifically and exclusively traced to a single project. The wages of an electrician working on that job are a direct labor cost. Office rent, bookkeeper salary, and software fees are considered indirect costs or overhead because they support the business's overall operations and are not tied to one specific project.

Question 21: When is an electrical permit generally NOT required?

Installing a backup generator transfer switch
Replacing a like-for-kind fixture in the same location (Correct answer)
Installing a new 200-amp service panel
Adding a new branch circuit in a commercial building

Correct answer: Replacing a like-for-kind fixture in the same location

Most jurisdictions exempt minor repairs and replacements—such as swapping a fixture in the same location—from permit requirements, though rules vary by jurisdiction.

Question 22: Which of the following best describes the OSHA requirement for 'Guarding of live parts' under 29 CFR 1926.403(i)(2)?

Live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact. (Correct answer)
All live parts must be de-energized before an employee works on or near them.
Guarding is only required in locations accessible to the general public, not on controlled construction sites.
Only live parts exceeding 120 volts require guarding by a permanent enclosure.

Correct answer: Live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact.

According to OSHA 29 CFR 1926.403(i)(2), live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact. This can be achieved by location in a room accessible only to qualified persons, by permanent partitions or screens, or by elevation of 8 feet or more above the floor.

Question 23: Which device provides both overload protection and short-circuit protection for a motor in a single assembly?

Combination motor controller (Correct answer)
Manual motor starter
Thermal overload relay
Fused disconnect switch

Correct answer: Combination motor controller

A combination motor controller integrates a disconnect means, overcurrent protection, and overload protection in one unit.

Question 24: When using an insulated aerial lift near energized lines, workers must maintain a minimum clearance of how many feet from lines under 50 kV?

10 feet (Correct answer)
15 feet
6 feet
3 feet

Correct answer: 10 feet

OSHA 29 CFR 1910.333 and NFPA 70E require at least 10 feet of clearance from unguarded energized lines up to 50 kV.

Question 25: Which transformer cooling designation indicates an oil-immersed, forced-oil-cooled, forced-air-cooled unit?

ONAF
ODAF
OFAF (Correct answer)
ONAN

Correct answer: OFAF

OFAF stands for Oil Forced (pumped oil circulation) / Air Forced (fans on radiators), distinguishing it from ONAN (natural oil, natural air convection cooling).

Question 26: On a three-phase motor, what is the effect of interchanging any two of the three supply phase conductors?

The motor will immediately draw locked rotor current
The motor will stop and fail to restart
The motor speed will increase above nameplate RPM
The direction of motor rotation will reverse (Correct answer)

Correct answer: The direction of motor rotation will reverse

Swapping any two of the three phase conductors feeding a three-phase induction motor reverses the rotating magnetic field and therefore reverses the direction of shaft rotation.

Question 27: Under NEC Article 626, electrolytic cells used in industrial processes must have their DC power supply disconnecting means able to de-energize the cell circuits within what maximum time?

Instantaneous (Correct answer)
30 seconds
10 seconds
5 seconds

Correct answer: Instantaneous

NEC 626.12 requires that the disconnecting means for electrolytic cell lines be capable of de-energizing them quickly enough to protect personnel, which means it must operate instantaneously.

Question 28: Which of the following best defines 'electrically safe work condition'?

Circuit breakers are in the off position but not locked out
Work is performed outside during daylight hours
All energy sources are locked out, tested de-energized, and grounded as required (Correct answer)
A qualified person is supervising the work at all times

Correct answer: All energy sources are locked out, tested de-energized, and grounded as required

An electrically safe work condition requires isolation, lockout, verification of de-energization, and grounding per NFPA 70E Article 120.

Question 29: What is Ohm's Law?

V = I × R. (Correct answer)
V = I ÷ R.
V = I - R.
V = I + R.

Correct answer: V = I × R.

Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. The formula V = I × R states that the voltage across a conductor is directly proportional to the current flowing through it, with the constant of proportionality being the resistance. This law is essential for analyzing and designing electrical systems.

Question 30: Why is it important to correctly size electrical wiring?

To increase the voltage of the circuit.
To save on the cost of materials.
To prevent overheating and potential hazards. (Correct answer)
To reduce the system's energy consumption.

Correct answer: To prevent overheating and potential hazards.

Correctly sizing electrical wiring is crucial to prevent overheating and potential hazards in an electrical system. Undersized wires can carry more current than they are safely rated for, leading to excessive heat generation, insulation damage, and a significant risk of electrical fires. Proper sizing ensures the wiring can safely handle the anticipated electrical load.

Question 31: What is the unit of electrical power?

Watts. (Correct answer)
Volts.
Ohms.
Amps.

Correct answer: Watts.

Watts (W) are the standard unit of measurement for electrical power, which quantifies the rate at which electrical energy is transferred or consumed. Power is calculated as the product of voltage and current (P = V × I). Understanding wattage is crucial for sizing electrical components and assessing energy consumption in various devices and systems.

Question 32: Which OSHA standard specifically governs electrical safety requirements for construction sites?

29 CFR 1910.303
29 CFR 1910.147
29 CFR 1926.100
29 CFR 1926.400 (Correct answer)

Correct answer: 29 CFR 1926.400

29 CFR 1926.400 (Subpart K) is OSHA's primary electrical safety standard for construction.

Question 33: Which OSHA standard primarily governs electrical safety in general industry workplaces?

29 CFR 1926.404
29 CFR 1910.145
29 CFR 1910.333 (Correct answer)
29 CFR 1926.501

Correct answer: 29 CFR 1910.333

29 CFR 1910.333 covers electrical safety-related work practices in general industry settings.

Question 34: What is the main difference between Class I, II, and III locations in electrical code?

They represent different types of materials used in electrical work.
They refer to different electrical voltages used.
They classify areas based on the potential for hazardous conditions. (Correct answer)
They represent different safety levels for electrical equipment.

Correct answer: They classify areas based on the potential for hazardous conditions.

Class I, II, and III locations in electrical code classify areas based on the potential for hazardous conditions due to the presence of flammable gases, combustible dusts, or ignitable fibers/flyings. This classification dictates the specific types of electrical equipment and wiring methods that must be used to ensure safety in environments where explosions or fires could occur. Understanding these distinctions is critical for safe electrical installations in industrial settings.

Question 35: A capacitor-start motor uses a run capacitor to improve efficiency. What does the run capacitor primarily improve?

Starting torque only
Insulation resistance
Power factor and running efficiency (Correct answer)
Locked-rotor current

Correct answer: Power factor and running efficiency

A run capacitor remains in the circuit during normal operation to correct power factor and improve running efficiency.

Question 36: Per NEC 220.14(I), what volt-ampere value is assigned to each single or duplex receptacle outlet for load calculation purposes?

120 VA
240 VA
90 VA
180 VA (Correct answer)

Correct answer: 180 VA

NEC 220.14(I) assigns 180 VA to each single or duplex receptacle outlet when calculating branch circuit and feeder loads.

Question 37: Per NEC Table 220.54, what is the demand factor for household electric dryers when 5 dryers are supplied from the same feeder?

100%
70%
50%
80% (Correct answer)

Correct answer: 80%

NEC Table 220.54 specifies an 80% demand factor when calculating feeder load for 5 household electric dryers.

Question 38: Which personal protective equipment (PPE) category under NFPA 70E requires an arc rating of at least 40 cal/cm²?

Category 1
Category 2
Category 4 (Correct answer)
Category 3

Correct answer: Category 4

NFPA 70E PPE Category 4 requires arc-rated clothing and equipment with a minimum arc rating of 40 cal/cm².

Question 39: Per NEC 110.3(B), listed or labeled equipment shall be installed and used in accordance with:

OSHA standards exclusively
The manufacturer's warranty only
Local municipality codes only
Any instructions included in the listing or labeling (Correct answer)

Correct answer: Any instructions included in the listing or labeling

NEC 110.3(B) requires that listed or labeled equipment be installed and used in accordance with any instructions included in the listing or labeling.

Question 40: The 'scope of practice' defined in an electrical contractor license refers to:

The geographic area in which the contractor may work
The types of electrical work the licensee is authorized to perform (Correct answer)
The dollar value of contracts the contractor may bid on
The number of employees the contractor may supervise at one time

Correct answer: The types of electrical work the licensee is authorized to perform

Scope of practice defines the category and type of electrical work a licensee is authorized to perform, which may differ between residential, commercial, and industrial classifications.

Question 41: According to NEC Article 525, temporary wiring for carnivals and fairs must use what minimum conductor size for branch circuits?

14 AWG
12 AWG (Correct answer)
8 AWG
10 AWG

Correct answer: 12 AWG

NEC 525.20(E) requires all branch circuit conductors for carnivals and fairs to be not smaller than 12 AWG.

Question 42: What information must an arc flash hazard label on electrical equipment include per NFPA 70E?

Manufacturer name, model number, and installation date
Nominal system voltage, arc flash boundary, and required PPE level or incident energy (Correct answer)
Circuit breaker ampere rating and interrupting capacity
Panel schedule reference and feeder conductor size

Correct answer: Nominal system voltage, arc flash boundary, and required PPE level or incident energy

NFPA 70E Section 130.5(H) requires labels to show voltage, arc flash boundary, and either incident energy or PPE category.

Question 43: In a health care facility critical branch, NEC 517.33 requires that the critical branch be transferred to alternate power within what maximum time after normal power failure?

20 seconds
60 seconds
30 seconds
10 seconds (Correct answer)

Correct answer: 10 seconds

NEC 517.33 requires the critical branch of a healthcare facility to be automatically transferred to alternate power within 10 seconds of normal power loss.

Question 44: Under OSHA's lockout/tagout standard (29 CFR 1910.147), when must an energy control procedure be documented in writing?

Only when more than 10 workers share the same equipment
Whenever the equipment is rated above 480V
When there is more than one energy source or the isolation is not readily apparent (Correct answer)
Only for equipment manufactured before 1990

Correct answer: When there is more than one energy source or the isolation is not readily apparent

Written procedures are required when equipment has more than one energy source or the lockout steps are not immediately obvious.

Question 45: Which OSHA standard requires employers to certify that personal protective equipment (PPE) has been provided, used, and maintained?

29 CFR 1910.132 (Correct answer)
29 CFR 1910.151
29 CFR 1926.28
29 CFR 1926.95

Correct answer: 29 CFR 1910.132

29 CFR 1910.132 requires employers to document PPE hazard assessments and certification that appropriate PPE has been selected.

Question 46: In a unit price contract, the contractor is paid based on:

Actual field-measured quantities times the agreed unit price (Correct answer)
A fixed total regardless of quantities
The original estimate quantities only
Cost plus a fixed percentage fee

Correct answer: Actual field-measured quantities times the agreed unit price

Under a unit price contract, final payment is calculated by multiplying actual field-measured quantities by the agreed unit prices for each bid item.

Question 47: What is the maximum number of disconnects permitted per service entrance under NEC 230.71?

4
2
6 (Correct answer)
8

Correct answer: 6

NEC 230.71(A) permits a maximum of six switches or sets of circuit breakers to serve as the service disconnecting means.

Question 48: A 20A, 120V branch circuit using 12 AWG THHN copper conductors has a run of 150 feet one-way. Approximately what is the voltage drop?

7.2V
3.6V
2.1V
5.4V (Correct answer)

Correct answer: 5.4V

Using VD = (2 × K × I × D) ÷ CM = (2 × 12.9 × 20 × 150) ÷ 6,530 ≈ 11.9V — but with 12 AWG at 20A for 150 ft, VD ≈ 5.4V, which exceeds the 3% recommendation (3.6V).

Question 49: Which document typically takes precedence in cases of conflict between the project drawings and the specifications?

Whichever document was issued more recently
The drawings always take precedence over specifications
The contract documents should specify the order of precedence; if silent, notes on drawings often govern (Correct answer)
The specifications always take precedence over drawings

Correct answer: The contract documents should specify the order of precedence; if silent, notes on drawings often govern

Most contracts establish a hierarchy in the order of precedence clause; absent that, most jurisdictions give precedence to more specific written specifications over graphic drawings.

Question 50: Which conductor insulation type is rated for use in wet locations AND has a 90°C temperature rating?

THWN-2 (Correct answer)
TW
THW
THHN

Correct answer: THWN-2

THWN-2 (Thermoplastic, Heat resistant, Water resistant, Nylon jacket, 2) is rated for wet locations at 90°C.

Question 51: What is the primary purpose of bonding in an electrical system?

To establish electrical continuity between conductive parts to eliminate voltage differences (Correct answer)
To reduce the grounding electrode resistance to earth
To provide a return path for fault current to the source
To protect equipment from lightning surges

Correct answer: To establish electrical continuity between conductive parts to eliminate voltage differences

Bonding ensures electrical continuity between conductive parts so no dangerous voltage differences exist between them.

Question 52: Per OSHA 29 CFR 1926.417, which action is required after a worker locks out equipment and before beginning work?

Attempt to operate the equipment to verify de-energization (Correct answer)
Notify the facility safety officer in writing
Post a danger sign near the equipment
Have a second worker verify the lockout tag

Correct answer: Attempt to operate the equipment to verify de-energization

OSHA requires workers to attempt to operate the equipment's normal controls after lockout to verify that it is actually de-energized.

Question 53: Per NEC 450.8, which marking must appear on a transformer nameplate?

Rated kVA, frequency, primary and secondary voltage, and impedance (Correct answer)
Only the primary voltage and kVA rating
Manufacturer's serial number and country of origin only
Maximum ambient temperature only

Correct answer: Rated kVA, frequency, primary and secondary voltage, and impedance

NEC 450.8 requires transformer nameplates to include rated kVA, frequency, primary and secondary voltage, impedance (on transformers 25 kVA and larger), and other information.

Question 54: What is 'locked rotor current' (LRC) in a motor circuit?

The steady-state running current at full load
The reduced current drawn at no-load speed
The high inrush current drawn when voltage is applied and the rotor has not yet begun turning (Correct answer)
The current drawn after the motor reaches synchronous speed

Correct answer: The high inrush current drawn when voltage is applied and the rotor has not yet begun turning

Locked rotor current is the maximum inrush current drawn from the supply when rated voltage is applied to a motor whose rotor is stationary.

Question 55: Which NEC article governs emergency systems used in hospitals and life safety applications?

Article 517
Article 700 (Correct answer)
Article 702
Article 701

Correct answer: Article 700

NEC Article 700 covers legally required emergency systems that provide power for egress lighting and life safety when normal power fails.

Question 56: What happens to inductive reactance (XL) when the frequency of the applied AC voltage doubles?

It halves
It doubles (Correct answer)
It stays the same
It quadruples

Correct answer: It doubles

XL = 2πfL; doubling frequency doubles XL since inductance L remains constant.

Question 57: NEC Article 501.105 specifies that luminaires in Class I, Division 1 locations must be marked to show the maximum wattage lamp permitted. Why is this marking required?

To indicate the luminaire's voltage rating
To satisfy insurance requirements
To comply with energy efficiency codes
To prevent overheating that could ignite the surrounding atmosphere (Correct answer)

Correct answer: To prevent overheating that could ignite the surrounding atmosphere

Overlamping a hazardous location luminaire can raise surface temperatures above the ignition temperature of flammable gases, so maximum wattage marking prevents this hazard.

Question 58: Which NFPA 70E article specifically addresses the requirements for establishing an electrically safe work condition?

Article 130
Article 110
Article 360
Article 120 (Correct answer)

Correct answer: Article 120

NFPA 70E Article 120 outlines the six-step process for establishing and verifying an electrically safe work condition.

Question 59: What is the maximum allowable distance between receptacles in a marina or boatyard pedestal installation per NEC Article 553?

The receptacle must be within 30 feet of the boat connection point (Correct answer)
No specific distance limit is specified in NEC 553
The receptacle must be within 15 feet of each slip
Each slip must have its own dedicated receptacle within 50 feet

Correct answer: The receptacle must be within 30 feet of the boat connection point

NEC 553.4 requires shore power receptacles to be located within 30 feet of the connected vessel to minimize cord hazards.

Question 60: In a project schedule created using the Critical Path Method (CPM), which of the following best describes the activities that make up the 'critical path'?

The first set of activities to be completed, such as site mobilization.
The tasks with the highest material costs.
The sequence of tasks that have zero 'float' or 'slack' time. (Correct answer)
All tasks that are performed by the electrical contractor.

Correct answer: The sequence of tasks that have zero 'float' or 'slack' time.

The Critical Path is the longest sequence of dependent tasks through the project schedule. Activities on this path have no slack or 'float,' meaning any delay in their execution will directly delay the overall project completion date.

Question 61: Three resistors of 6Ω, 12Ω, and 4Ω are connected in parallel. What is the total equivalent resistance?

2 Ω (Correct answer)
1.5 Ω
22 Ω
7.33 Ω

Correct answer: 2 Ω

1/R_T = 1/6 + 1/12 + 1/4 = 2/12 + 1/12 + 3/12 = 6/12, so R_T = 2Ω.

Question 62: A state electrical contractor license is typically renewed every:

5 years uniformly across all states
Only once, since licenses are issued for life after passing the exam
6 months
1 year or 2 years depending on the state (Correct answer)

Correct answer: 1 year or 2 years depending on the state

License renewal periods vary by state, with one- or two-year cycles being the most common, often requiring continuing education and a renewal fee.

Question 63: What is the primary cause of eddy current losses in transformer cores?

AC magnetic flux inducing circulating currents within the core material (Correct answer)
High winding resistance
Insulation breakdown between windings
Excessive cooling oil temperature

Correct answer: AC magnetic flux inducing circulating currents within the core material

Alternating magnetic flux induces voltages in the iron core, driving circulating (eddy) currents that produce heat.

Question 64: Per NEC 230.24(B), what is the minimum clearance required for service drop conductors above public streets subject to truck traffic?

22 feet
12 feet
18 feet (Correct answer)
15 feet

Correct answer: 18 feet

NEC 230.24(B) requires service drop conductors to maintain at least 18 feet of clearance above public streets, alleys, roads, and driveways subject to truck traffic.

Question 65: Which NFPA standard specifically addresses electrical safety in the workplace?

NFPA 101
NFPA 72
NFPA 70E (Correct answer)
NFPA 70B

Correct answer: NFPA 70E

NFPA 70E covers electrical safety requirements for employee workplaces, including arc flash hazard analysis.

Question 66: Which NEC article covers service conductors and equipment for electrical services?

Article 240
Article 230 (Correct answer)
Article 225
Article 220

Correct answer: Article 230

NEC Article 230 covers service conductors and service entrance equipment including disconnecting means and overcurrent protection.

Question 67: For a solar photovoltaic (PV) system installed on a building, what are the requirements for rapid shutdown for controlled conductors located MORE than 3 feet from the point of entry inside the building?

They are not subject to rapid shutdown requirements.
They must be de-energized to 0 volts within 10 seconds of shutdown initiation.
They must be limited to not more than 80 volts within 60 seconds of shutdown initiation.
They must be limited to not more than 30 volts within 30 seconds of shutdown initiation. (Correct answer)

Correct answer: They must be limited to not more than 30 volts within 30 seconds of shutdown initiation.

NEC 690.12 specifies the requirements for the rapid shutdown of PV systems on buildings to reduce shock hazards for emergency responders. For controlled conductors located outside the array boundary or more than 3 feet from the point of entry into the building, the voltage must be limited to not more than 30 volts within 30 seconds of initiating the rapid shutdown.

Question 68: Per NEC 310.15, what ambient temperature correction factor applies to THHN conductors when the ambient temperature is 50°C?

0.58 (Correct answer)
0.71
0.91
0.82

Correct answer: 0.58

THHN is rated for 90°C; at 50°C ambient, the correction factor from NEC Table 310.15(B)(1) is 0.58.

Question 69: What is the purpose of the supply-side bonding jumper (SSBJ) in an electrical system?

To connect the grounded conductor on the supply side of a disconnecting means to the equipment grounding conductor (Correct answer)
To bond the neutral bus to the chassis of the main panel
To reduce touch voltage at the service entrance
To bond all metal water piping on the load side

Correct answer: To connect the grounded conductor on the supply side of a disconnecting means to the equipment grounding conductor

The SSBJ connects the grounded (neutral) conductor on the supply side of a service disconnect to the EGC, ensuring fault current return paths for separately derived systems.

Question 70: Under NEC 250.119, which color or marking identifies an equipment grounding conductor for conductors larger than #6 AWG?

Green insulation only
Bare copper only
Green tape, green paint, or other green marking at terminations (Correct answer)
White or gray insulation

Correct answer: Green tape, green paint, or other green marking at terminations

For EGCs larger than #6 AWG, NEC 250.119 allows identification by green tape, green paint, or other green marking at every point where the conductor is accessible.

Question 71: What is the minimum ampere rating for service entrance equipment in a new single-family dwelling per NEC 230.79(C)?

60 amperes
200 amperes
150 amperes
100 amperes (Correct answer)

Correct answer: 100 amperes

NEC 230.79(C) requires that the service disconnecting means for a single-family dwelling be rated at not less than 100 amperes.

Question 72: What must an electrical contractor do when a near-miss incident occurs on a job site?

File an OSHA 300 log entry within 7 days
Document it, investigate root causes, and implement corrective actions to prevent recurrence (Correct answer)
Report it only if it resulted in property damage exceeding $1,000
Notify the electrical inspector and cease all work until cleared

Correct answer: Document it, investigate root causes, and implement corrective actions to prevent recurrence

Near-miss incidents are leading indicators of future accidents and must be investigated and corrected to improve safety culture.

Question 73: Per NEC 547.9, the disconnecting means for agricultural buildings must be located outside the building or inside near the point of entry. What is the maximum number of disconnects permitted as the service disconnecting means?

No limit specified
4
6 (Correct answer)
2

Correct answer: 6

NEC 230.71 permits a maximum of six disconnects as the service disconnecting means, which also applies to agricultural buildings under Article 547.

Question 74: A contractor submits a schedule of values at the start of a project. What is the primary purpose of this document?

To establish the sequence in which work will be performed
To identify which materials will be procured first
To allocate the contract price among work components for progress payment purposes (Correct answer)
To list the subcontractors who will perform each scope of work

Correct answer: To allocate the contract price among work components for progress payment purposes

A schedule of values breaks down the contract sum into component line items so that progress payments can be calculated based on percentage of completion for each item.

Question 75: What does NEMA MG1 classify regarding motor construction?

Motor winding insulation classes only
Motor voltage and frequency ratings only
Motor starting torque categories only
Motor enclosure types such as ODP and TEFC (Correct answer)

Correct answer: Motor enclosure types such as ODP and TEFC

NEMA MG1 is the standard that classifies motor enclosure types including Open Drip Proof (ODP) and Totally Enclosed Fan Cooled (TEFC) among others.

Question 76: What is the difference between alternating current (AC) and direct current (DC)?

AC reverses direction periodically; DC flows in one direction.
AC and DC are the same.
AC flows in one direction; DC reverses direction periodically.
AC flows in one direction; DC flows in one direction. (Correct answer)

Correct answer: AC flows in one direction; DC flows in one direction.

Alternating Current (AC) is characterized by its periodic reversal of direction, meaning the current flow changes back and forth. In contrast, Direct Current (DC) flows consistently in a single direction. This fundamental difference in current behavior dictates how electricity is generated, transmitted, and used in various applications, from household outlets (AC) to batteries (DC).

Question 77: What NEC section governs the bonding of metal gas piping systems in a building?

NEC 250.52
NEC 250.64
NEC 250.28
NEC 250.104(B) (Correct answer)

Correct answer: NEC 250.104(B)

NEC 250.104(B) requires metal gas piping to be bonded to the electrical service equipment, the grounded conductor, or the grounding electrode conductor.

Question 78: What is the minimum size equipment grounding conductor (EGC) required for a circuit protected by a 100A overcurrent device per NEC Table 250.122?

#4 AWG copper
#6 AWG copper
#8 AWG copper (Correct answer)
#10 AWG copper

Correct answer: #8 AWG copper

Per NEC Table 250.122, a 100A overcurrent device requires a minimum #8 AWG copper equipment grounding conductor.

Question 79: If a 120V outlet supplies a 1,440W load, what is the current draw?

12 A (Correct answer)
120 A
8 A
16 A

Correct answer: 12 A

I = P / V = 1,440 / 120 = 12 A.

Question 80: When installing a panelboard in a bathroom of a dwelling unit, what does the NEC prohibit?

Use of copper conductors
Installing GFCI breakers
Panelboard installation entirely (Correct answer)
Overcurrent protection above 15A

Correct answer: Panelboard installation entirely

NEC 240.24(E) prohibits overcurrent devices from being located in bathrooms of dwelling units, guest rooms, or guest suites.

Question 81: The synchronous speed of a 4-pole induction motor operating on a 60Hz system is:

3,600 RPM
900 RPM
1,800 RPM (Correct answer)
1,200 RPM

Correct answer: 1,800 RPM

Ns = (120 × f) / P = (120 × 60) / 4 = 1,800 RPM.

Question 82: When two 100 µF capacitors are connected in series, what is the total capacitance?

100 µF
25 µF
200 µF
50 µF (Correct answer)

Correct answer: 50 µF

For equal capacitors in series, C_T = C/n = 100/2 = 50 µF.

Question 83: What is an arc flash, and how can it be mitigated?

An arc flash is a sudden electrical discharge, mitigated by using proper safety procedures and PPE. (Correct answer)
An arc flash is caused by worn-out wires only.
An arc flash is caused by poor ventilation in electrical rooms.
An arc flash is a fire caused by electrical current.

Correct answer: An arc flash is a sudden electrical discharge, mitigated by using proper safety procedures and PPE.

An arc flash is a dangerous electrical explosion that occurs when an electrical current leaves its intended path and travels through the air, creating a high-energy discharge. This event generates intense heat, light, and pressure waves, posing severe burn and blast hazards. Mitigation involves strict adherence to safety procedures, such as de-energizing equipment, and the use of specialized arc-rated Personal Protective Equipment (PPE) to shield workers from its devastating effects.

Question 84: A series circuit has resistors of 10Ω, 20Ω, and 30Ω connected to a 120V source. What is the total current in the circuit?

6A
4A
1A
2A (Correct answer)

Correct answer: 2A

Total resistance = 10+20+30 = 60Ω; I = V/R = 120/60 = 2A.

Question 85: Which statement about voltage drops in a series circuit is correct?

The largest resistor has the smallest voltage drop
All resistors have equal voltage drops
Voltage drop is independent of resistance
Voltage drops are proportional to resistance values (Correct answer)

Correct answer: Voltage drops are proportional to resistance values

In a series circuit, voltage drops are proportional to each resistor's value relative to total resistance.

Question 86: What NEC article governs branch circuits?

Article 200
Article 230
Article 220
Article 210 (Correct answer)

Correct answer: Article 210

NEC Article 210 covers branch circuits, including their ratings, outlets, and required circuits.

Question 87: What does the term 'addendum' refer to during the bidding process?

A change order after contract award
A contractor's request for information
A written modification issued to all bidders before bid opening (Correct answer)
A supplemental insurance certificate

Correct answer: A written modification issued to all bidders before bid opening

An addendum is a written modification to the bidding documents issued by the owner or architect to all bidders before the bid deadline.

Question 88: Three resistors of 6Ω, 12Ω, and 4Ω are connected in parallel. What is the total equivalent resistance?

2Ω (Correct answer)
0.5Ω
7.3Ω
22Ω

Correct answer: 2Ω

1/Rt = 1/6 + 1/12 + 1/4 = 2/12 + 1/12 + 3/12 = 6/12; Rt = 2Ω.

Question 89: What is the standard secondary voltage for a motor control circuit transformer per NEC 430.72?

600V
480V
240V
120V (Correct answer)

Correct answer: 120V

NEC 430.72 permits control circuit conductors supplied by a grounded transformer secondary at up to 120V without additional overcurrent protection in many cases.

Question 90: A step-up transformer increases voltage. To maintain conservation of energy, it must correspondingly:

Decrease frequency on the secondary side
Increase resistance on the primary side
Increase current on the secondary side
Decrease current on the secondary side (Correct answer)

Correct answer: Decrease current on the secondary side

Since power = V × I must be conserved (in an ideal transformer), increasing voltage requires a proportional decrease in current.

Question 91: In the electrical estimating process, what is the primary purpose of performing a quantity takeoff?

To finalize the project completion schedule.
To negotiate material pricing with suppliers.
To determine the final contract price including profit.
To systematically identify and count all required materials and labor units from the plans. (Correct answer)

Correct answer: To systematically identify and count all required materials and labor units from the plans.

A quantity takeoff is the process of meticulously reviewing project documents (drawings and specifications) to identify and quantify every component required for the job. This includes counting fixtures, measuring conduit and wire runs, and identifying all other materials and the labor associated with them. This list forms the foundation for all subsequent steps like pricing, scheduling, and applying profit.

Question 92: A 240V, single-phase motor nameplate shows 18A full-load current. What is the minimum branch circuit conductor ampacity required?

18A
22.5A (Correct answer)
20A
25A

Correct answer: 22.5A

Per NEC 430.22, branch circuit conductors for a single motor must have an ampacity of at least 125% of the motor's full-load current: 18A × 1.25 = 22.5A.

Question 93: What are lockout/tagout procedures in electrical safety?

A method of protecting workers by marking equipment.
A process for repairing faulty equipment.
A method for reducing energy consumption.
A method of de-energizing electrical systems to protect workers during maintenance. (Correct answer)

Correct answer: A method of de-energizing electrical systems to protect workers during maintenance.

Lockout/Tagout (LOTO) procedures are essential safety protocols designed to prevent accidental energization of machinery or equipment during maintenance or servicing. This involves physically locking off power sources and placing a tag on the energy-isolating device, indicating that the equipment is being worked on and should not be re-energized. LOTO ensures that workers are protected from unexpected startups or the release of hazardous energy, preventing serious injuries or fatalities.

Question 94: Under OSHA 29 CFR 1910.305(j), flexible cords and cables used as a substitute for fixed wiring are:

Allowed only in residential applications
Prohibited and must be replaced with permanent wiring (Correct answer)
Permitted when protected by a GFCI
Permitted if rated for hard usage

Correct answer: Prohibited and must be replaced with permanent wiring

OSHA prohibits using flexible cords and cables as substitutes for permanent fixed wiring in any workplace.

Question 95: Which of the following wiring methods is approved for use in a Class I, Division 1 hazardous location?

Liquidtight flexible nonmetallic conduit
Electrical metallic tubing (EMT)
Type MC-HL cable (Correct answer)
Type NM cable

Correct answer: Type MC-HL cable

Type MC-HL (Hazardous Location) cable is specifically listed for Class I, Division 1 locations per NEC 501.10.

Question 96: Which NEC article governs the installation and protection of transformers?

Article 410
Article 480
Article 450 (Correct answer)
Article 230

Correct answer: Article 450

NEC Article 450 covers transformers, including overcurrent protection, installation requirements, and marking.

Question 97: In a health care facility, which grounding system is required in patient care areas to minimize leakage current?

Ungrounded (IT) power system for all receptacles
Double-pole grounding system
Patient equipment grounding point (PEGP) with redundant EGC paths (Correct answer)
Isolated ground receptacles on all circuits

Correct answer: Patient equipment grounding point (PEGP) with redundant EGC paths

NFPA 99 and NEC 517 require patient equipment grounding points providing redundant low-impedance EGC paths to protect patients from microshock hazards.

Question 98: OSHA defines an 'authorized employee' under the lockout/tagout standard as someone who:

Has been employed for more than 90 days
Works in the same area as the equipment being serviced
Locks out or tags out machines to perform servicing or maintenance (Correct answer)
Has been trained to recognize hazardous energy sources

Correct answer: Locks out or tags out machines to perform servicing or maintenance

An authorized employee is the worker who actually applies the lockout/tagout device to control hazardous energy.

Question 99: Which of the following wiring methods is generally NOT permitted for wiring within an elevator hoistway, according to NEC Article 620?

Electrical metallic tubing (EMT).
Intermediate metal conduit (IMC).
Rigid metal conduit (RMC).
Type NM (Nonmetallic-sheathed) cable. (Correct answer)

Correct answer: Type NM (Nonmetallic-sheathed) cable.

NEC Article 620 specifies acceptable wiring methods for elevators, hoistways, and machine rooms. Permitted methods include robust options like RMC, IMC, and EMT. Type NM cable is generally prohibited in these locations due to lack of physical protection and specific flame-retardant characteristics required for these environments.

Question 100: Per NEC Table 220.42, what demand factor applies to the first 3,000 VA of residential lighting load?

125%
100% (Correct answer)
50%
75%

Correct answer: 100%

NEC Table 220.42 specifies a 100% demand factor for the first 3,000 VA of residential lighting load; demand factors drop for additional load.

NASCLA Accredited Professional Electrical Contractor Exam

The NASCLA Accredited Professional Electrical Contractor (Master/Unlimited) exam tests knowledge of the National Electrical Code (NEC), electrical theory, wiring methods, equipment, safety standards, and project management required for electrical contractor licensure. It is an open-book examination accepted by multiple state licensing boards.

100

Questions

270 min

Time Limit

75%

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