Free NEC Electrical Questions and Answers 1 — Questions and Answers

Question 1: Metal water pipes shall be bonded to _____ when they are put in or attached to a building or structure.

the grounded conductor at the service
the grounding electrode conductor
the service equipment enclosure
any of the following (Correct answer)

Correct answer: any of the following

NEC 250.104(A)(1) mandates that metal water piping systems installed in or attached to a building or structure must be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor, or one or more grounding electrodes used. This comprehensive bonding ensures that all conductive parts are at the same electrical potential, preventing dangerous voltage differences during a ground fault and minimizing the risk of electric shock.

Question 2: When Type AC armored cable is installed parallel to the sides of rafters, studs, or floor joists in an accessible attic, .

the cable shall be protected by guard strips at least as high as the cable
neither guard strips nor running boards shall be required (Correct answer)
either A or B
the cable shall be protected with running boards

Correct answer: neither guard strips nor running boards shall be required

NEC 320.23(A)(2) specifies that when Type AC armored cable is installed in an accessible attic and run parallel to the sides of rafters, studs, or floor joists, neither guard strips nor running boards are required. In this orientation, the cable is considered sufficiently protected by its proximity to the structural members. This simplifies installation while still ensuring adequate protection against physical damage.

Question 3: The manual switch for controlling the emergency lighting systems in a movie theater is usually permitted to be located .

in the motion picture projection booth
on the stage or platform
in an accessible location in the lobby (Correct answer)
at any of these locations

Correct answer: in an accessible location in the lobby

NEC 700.20 requires switches for emergency lighting to be accessible only to authorized persons. For places of assembly like movie theaters, the manual switch for controlling emergency lighting systems is typically permitted in an accessible location in the lobby. This placement ensures that authorized personnel can quickly activate or test the system in an emergency, while also being in a controlled environment to prevent unauthorized tampering.

Question 4: For use in PV source circuits within the PV array, single-conductor cable such as _____ and single-conductor cable listed and labeled as solar photovoltaic (PV) wire are permitted.

THHN
PVC-2
UF
USE-2 (Correct answer)

Correct answer: USE-2

NEC 690.31(C) permits the use of specific single-conductor cables, such as Type USE-2, Type RHW-2, Type XHHW-2, and single-conductor cable listed and labeled as solar photovoltaic (PV) wire, for PV source circuits within the PV array. These cable types are designed to withstand the harsh outdoor conditions, including UV exposure, moisture, and temperature extremes, ensuring the durability and safety required for photovoltaic installations.

Question 5: All single-phase, 125-volt, 15- and 20-ampere receptacles installed within six (6) feet of the top inside edge of the bowl of sinks located in _____, must have GFCI protection for dwelling units.

garages
bathrooms
laundry rooms
all of these areas (Correct answer)

Correct answer: all of these areas

NEC 210.8(A)(7) mandates GFCI protection for all 125-volt, single-phase, 15- and 20-ampere receptacles installed within 6 feet of the top inside edge of the bowl of a sink in dwelling unit bathrooms, garages, laundry areas, utility rooms, basements, and wet bar sinks. This comprehensive requirement ensures crucial protection against electric shock in various wet and potentially hazardous areas within a dwelling unit.

Question 6: If ground-fault protection is not provided, it is permitted to ground the meter enclosure to the ____________ conductor on the load side of the service disconnect for a building or structure when the meter enclosure is adjacent to the service disconnecting.

grounding
phase
grounded (Correct answer)
bonding

Correct answer: grounded

NEC 250.84(B) permits grounding the meter enclosure to the grounded (neutral) conductor on the load side of the service disconnect for a building or structure, provided the meter enclosure is adjacent to the service disconnecting means and ground-fault protection is not provided. This alternative grounding method ensures the enclosure is maintained at the same potential as the system neutral, providing a safe path for fault current and minimizing shock hazards.

Question 7: The maximum permissible cord-and-plug-attached load to a 125-volt, 15-ampere receptacle connected to a 120-volt branch circuit supplying two (2) or more receptacles or outlets is .

10 amperes
12 amperes (Correct answer)
7.5 amperes
15 amperes

Correct answer: 12 amperes

According to NEC 210.23(A)(1), the total rating of cord-and-plug-connected utilization equipment not fastened in place shall not exceed 80% of the branch-circuit ampere rating. For a 15-ampere branch circuit, 80% of 15 amperes is 12 amperes. This limit ensures a safety margin, preventing continuous overloading of the circuit and allowing for other potential loads without tripping the overcurrent device.

Question 8: When a 200-ampere rated busway is tapped from a 600-ampere rated busway in industrial facilities only, what is the maximum permitted length of the 200-ampere busway if overcurrent protection is not provided for the 200-ampere busway?

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

Correct answer: 50 feet

NEC 368.17(C) allows for taps from busways in industrial establishments. When a 200-ampere busway is tapped from a 600-ampere busway (meeting the one-third ampacity rule), the tap busway can be a maximum of 50 feet (15 meters) long without requiring additional overcurrent protection at the tap point. This rule provides flexibility in industrial wiring while ensuring adequate protection against overloads and short circuits for the tap conductors.

Question 9: In the case of a commercial building, each of the four (4) size 2 AWG THWN insulated copper current-carrying conductors in a service-entrance conduit with a length of six (6) feet has an allowable ampacity of.

100 amperes
115 amperes
110 amperes
92 amperes (Correct answer)

Correct answer: 92 amperes

To determine the allowable ampacity, we first find the base ampacity for 2 AWG THWN copper conductor from NEC Table 310.16, which is 115 A (75°C column). Since there are four current-carrying conductors in the conduit and the length exceeds 24 inches, an adjustment factor for conductor bundling is required. According to NEC Table 310.15(B)(3)(a), for 4-6 conductors, the ampacity is adjusted by 80%, resulting in an allowable ampacity of 115 A * 0.80 = 92 A.

Question 10: Which of the following can be supplied by circuits with a maximum nominal voltage between conductors of 120 volts?

The terminals of lampholders applied within their voltage ratings
Auxiliary equipment of electric-discharge lamps.
Cord-and-plug-connected or permanently connected utilization equipment
All of the above (Correct answer)

Correct answer: All of the above

NEC 210.6(A) specifies the types of equipment that can be supplied by branch circuits with a maximum nominal voltage of 120 volts between conductors. This includes the terminals of lampholders applied within their voltage ratings, auxiliary equipment of electric-discharge lamps, and both cord-and-plug-connected or permanently connected utilization equipment. This section ensures that equipment is connected to circuits within its design voltage limits, promoting safe and proper operation.

Question 11: When installing cable or raceway-style wiring in visible or concealed places through bored holes in joists, rafters, or other wood members, the edge of the hole must be at least _ inches from the closest edge of the wood member. Where the required distance cannot be achieved, a steel bushing or plate that is at least _ inches thick and that is installed to cover the area where the wiring is located must be used to prevent nails or screws from penetrating the cable or raceway.

1.5" | 0.125"
1.75" | 0.25"
1.25" | 0.0625" (Correct answer)
1.625 | 0.20"

Correct answer: 1.25" | 0.0625"

This question refers to the NEC requirement for protecting cables and raceways in wood framing. Article 300.4(A)(1) mandates that bored holes must be at least 1.25 inches from the nearest edge of the wood member to prevent penetration by nails or screws. If this distance cannot be maintained, a steel plate or bushing at least 0.0625 inches (1/16 inch) thick must be installed to provide equivalent protection, safeguarding the wiring from damage.

Question 12: When a ground-fault current exceeds the limits set for a Class A device, a mechanism designed to safeguard employees can de-energize a circuit or a section of it within a set amount of time.

Electronically Activated Fuse
Arc-Fault Circuit Interrupter (AFCI)
Separately Derived System
Ground-Fault Circuit Interrupter (GFCI) (Correct answer)

Correct answer: Ground-Fault Circuit Interrupter (GFCI)

A Ground-Fault Circuit Interrupter (GFCI) is specifically designed to protect people from electric shock by detecting small imbalances in current flow, indicating a ground fault. When the ground-fault current exceeds a predetermined limit (typically 5 mA for Class A devices), the GFCI rapidly de-energizes the circuit. This swift action safeguards employees and occupants by preventing sustained exposure to hazardous ground-fault currents.

Question 13: All switches and circuit breakers that are used as switches must be installed so that the operating handle is not more than _________ above the working platform or floor when it is in its highest position.

6 ft
7 ft
5 ft 6 in.
6 ft 7 in. (Correct answer)

Correct answer: 6 ft 7 in.

NEC Article 404.8(A) specifies the maximum height for the operating handle of switches and circuit breakers used as switches. To ensure accessibility and safe operation for most individuals, the highest position of the handle must not exceed 6 feet 7 inches (2.0 m) above the working platform or floor. This standard helps prevent injuries and ensures that electrical controls are within reach for emergency shut-off or routine operation.

Question 14: What is the maximum permitted voltage between conductors on a branch circuit serving luminaires in a residence?

240 volts
120 volts (Correct answer)
250 volts
150 volts

Correct answer: 120 volts

For branch circuits supplying luminaires (lighting fixtures) in a residence, the maximum permitted voltage between conductors is 120 volts. This is a fundamental safety standard in residential wiring, as most common household lighting and receptacle outlets are designed for 120-volt operation. Adhering to this voltage limit minimizes shock hazards and ensures compatibility with standard residential equipment.

Question 15: The same _________ shall contain all conductors of the same circuit, the grounded conductor when used, and all equipment grounding conductors and bonding conductors.

raceway (Correct answer)
pipe
conduit
channel

Correct answer: raceway

NEC Article 300.3(B) mandates that all conductors of the same circuit, including the grounded conductor (if used) and all equipment grounding and bonding conductors, must be contained within the same raceway, cable, trench, cable tray, or cord. This requirement, known as the 'all conductors in the same raceway' rule, is crucial for preventing inductive heating and ensuring proper operation of overcurrent protective devices. It ensures that magnetic fields generated by current-carrying conductors cancel each other out, reducing impedance and maintaining safety.

Question 16: An institution, office, or person in charge of upholding a code or standard's standards or of authorizing tools, supplies, setups, or procedures.

Building and Safety Department (BSD)
National Building Authority (NBA)
Authority Having Jurisdiction (AHJ) (Correct answer)
Code Enforcement Agency (CEA)

Correct answer: Authority Having Jurisdiction (AHJ)

The Authority Having Jurisdiction (AHJ) is the entity responsible for enforcing the provisions of the National Electrical Code (NEC) and other building codes. This term refers to the organization, office, or individual empowered to approve equipment, materials, installations, or procedures. The AHJ plays a critical role in ensuring electrical safety by inspecting installations and verifying compliance with established standards.

Free NEC Electrical Questions and Answers 1

Metal water pipes shall be bonded to _____ when they are put in or attached to a building or structure.

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