Certified Master Electrician (CME) Exam — Questions and Answers

Question 1: A designer specifies a bus duct (busway) system for a 2000A, 480V, 3-phase distribution. What NEC article governs busway installation?

Article 362
Article 366
Article 368 (Correct answer)
Article 376

Correct answer: Article 368

NEC Article 368 covers busways (bus ducts), including installation requirements, supports, overcurrent protection, and permitted uses for high-capacity distribution systems.

Question 2: What is the minimum size copper equipment grounding conductor (EGC) required for a circuit protected by a 100A overcurrent device per NEC Table 250.122?

6 AWG
8 AWG (Correct answer)
4 AWG
2 AWG

Correct answer: 8 AWG

NEC Table 250.122 specifies a minimum 8 AWG copper EGC for circuits protected by overcurrent devices rated up to 100A.

Question 3: How can electrical systems be designed to minimize maintenance?

By using fewer circuits.
By increasing system complexity.
By limiting the system's power output.
By using high-quality components and ensuring easy maintenance. (Correct answer)

Correct answer: By using high-quality components and ensuring easy maintenance.

Electrical systems can be designed to minimize maintenance by prioritizing the use of high-quality, durable components that are less prone to failure and degradation over time. Additionally, incorporating features that allow for easy access, clear labeling, and modular design simplifies routine inspections and repairs. This thoughtful design approach reduces the frequency and complexity of maintenance tasks, leading to greater reliability and lower long-term operational costs.

Question 4: A master electrician is supervising a team performing maintenance on a large motor control center with multiple sources of power. The procedure requires several disconnects to be opened and locked out. According to NFPA 70E, what type of lockout/tagout procedure is required in this scenario?

A simple lockout/tagout procedure.
An individual lockout/tagout procedure.
A group lockout/tagout procedure.
A complex lockout/tagout procedure. (Correct answer)

Correct answer: A complex lockout/tagout procedure.

NFPA 70E specifies that a complex lockout/tagout procedure is required when there are multiple energy sources, multiple crews, multiple disconnecting means, or the job extends for more than one work period. This scenario involves multiple sources and disconnects, mandating a written plan and a person in charge to coordinate the effort safely.

Question 5: Per NEC 250.30, where must the system bonding jumper be installed for a separately derived system?

At the main service disconnect of the building
At the first disconnecting means only
At both the source and at each distribution panel
At the source of the separately derived system (Correct answer)

Correct answer: At the source of the separately derived system

NEC 250.30(A)(1) requires the system bonding jumper to be installed at the source of the separately derived system to connect the grounded conductor to the equipment grounding conductor.

Question 6: What is the calculated demand load for a single 14 kW household electric range on a branch circuit?

8.0 kW
8.8 kW
14 kW
8.4 kW (Correct answer)

Correct answer: 8.4 kW

Per NEC Table 220.55, Column C, the demand for one range up to 12 kW is 8 kW. Note 1 applies to ranges over 12 kW. The demand must be increased by 5% for each kilowatt exceeding 12 kW. This range is 14 kW, which is 2 kW over 12 kW. Therefore, the percentage increase is 2 × 5% = 10%. The demand load is the base demand from Column C plus the increase: 8 kW + (10% of 8 kW) = 8 kW + 0.8 kW = 8.8 kW.

Question 7: A variable frequency drive (VFD) display shows an 'overcurrent' fault immediately at startup. The motor has been recently rewound. What should be checked FIRST?

The input supply voltage to the VFD
The acceleration ramp time setting in the VFD (Correct answer)
Whether the rewound motor's full-load amps match the VFD rating
The VFD output frequency setting

Correct answer: The acceleration ramp time setting in the VFD

A too-short acceleration ramp time causes the VFD to demand high current rapidly during startup; increasing the acceleration time is the first adjustment to make before assuming a motor or drive fault.

Question 8: A multi-family building has 40 electric ranges rated at 12 kW each. Per NEC Table 220.55, Column C, what is the total demand load?

55 kW (Correct answer)
67 kW
Both A and B are correct
55,000 VA

Correct answer: 55 kW

NEC Table 220.55 Column C for 40 ranges gives a maximum demand of 55 kW.

Question 9: What is the primary legal significance of the NEC being adopted by a state or local jurisdiction?

It becomes a recommendation that contractors should follow
It becomes enforceable law within that jurisdiction (Correct answer)
It replaces OSHA standards in that jurisdiction
It applies only to federally funded projects

Correct answer: It becomes enforceable law within that jurisdiction

Once a jurisdiction adopts the NEC through legislation or ordinance, compliance becomes legally mandatory and enforceable by the AHJ.

Question 10: A master electrician is designing a multi-building campus distribution system. Which grounding method is required when a feeder extends to a separate building with its own disconnect per NEC 250.32?

A grounding electrode system must be installed at the separate building (Correct answer)
The grounding electrode conductor must run back to the main building
A separate utility ground rod is required at each building
The neutral must be re-bonded at the separate building disconnect

Correct answer: A grounding electrode system must be installed at the separate building

NEC 250.32(A) requires a grounding electrode system to be connected to the disconnecting means at a separate structure supplied by a feeder or branch circuit.

Question 11: NEC 517.20 requires what protection for receptacles and fixed equipment in wet procedure locations of healthcare facilities?

AFCI protection only
Isolated power system or GFCI protection (Correct answer)
Double-insulated equipment exclusively
Explosionproof outlets

Correct answer: Isolated power system or GFCI protection

NEC 517.20 requires wet procedure locations to use either an isolated power system or GFCI protection to safeguard patients from electric shock.

Question 12: Which test instrument is MOST appropriate for verifying the operation of an arc fault circuit interrupter (AFCI)?

A clamp-on ammeter measuring leakage current
A megohmmeter set to 500V DC
A dedicated AFCI circuit tester with a test button (Correct answer)
A phase rotation meter

Correct answer: A dedicated AFCI circuit tester with a test button

A dedicated AFCI tester simulates the specific arc fault waveform signature required to trip an AFCI breaker, which standard outlet testers cannot do.

Question 13: A 3-phase, 480V motor has a full-load current (FLC) of 65A per Table 430.250. The branch circuit will be protected by an inverse-time circuit breaker. According to NEC 430.52(C)(1), what is the MAXIMUM standard size circuit breaker permitted for short-circuit and ground-fault protection?

200A
150A
175A (Correct answer)
125A

Correct answer: 175A

NEC Table 430.52 specifies the maximum rating for a motor branch-circuit short-circuit and ground-fault protective device. For an inverse-time circuit breaker, this is 250% of the motor's FLC. Calculation: 65A (FLC) x 250% = 162.5A. According to 430.52(C)(1) Exception No. 1, if the calculated value does not correspond to a standard size listed in 240.6(A), the next higher standard size is permitted. The next standard size above 162.5A is 175A.

Question 14: A building energy audit identifies that replacing T12 fluorescent fixtures with LED equivalents will reduce lighting load by 40%. What additional NEC requirement applies to the new LED drivers?

LED drivers require a dedicated 20A circuit each
LED drivers must be installed in weatherproof enclosures
LED drivers must be rated for 277V minimum in commercial applications
LED drivers must be listed for the specific luminaire per NEC 410.6 (Correct answer)

Correct answer: LED drivers must be listed for the specific luminaire per NEC 410.6

NEC 410.6 requires that luminaires, lampholders, and associated drivers be listed for their intended use to ensure safety and compatibility.

Question 15: NEC 680.8 specifies the minimum clearance for overhead service conductors above the water surface of a swimming pool as:

22.5 feet (Correct answer)
14.5 feet
25 feet
10 feet

Correct answer: 22.5 feet

NEC 680.8(A) requires a minimum 22.5-foot vertical clearance for overhead service conductors above a pool's water surface to prevent contact hazards.

Question 16: According to NFPA 70E and OSHA standards, which of the following is a primary requirement for an individual to be considered a "Qualified Person"?

Having received safety training to identify and avoid electrical hazards and demonstrating related skills and knowledge. (Correct answer)
Holding a valid master electrician license for at least five years.
Being designated in writing by the site's general contractor.
Successfully passing a company-specific written examination on electrical theory.

Correct answer: Having received safety training to identify and avoid electrical hazards and demonstrating related skills and knowledge.

Both NFPA 70E and OSHA define a qualified person as someone who has received safety training to identify and reduce the associated risks of electrical hazards and has demonstrated the skills and knowledge related to the construction and operation of the electrical equipment. While licensure and exams can be part of the qualification process, the core requirement is the specific training and demonstrated ability to work safely around the hazards involved.

Question 17: What is the purpose of a contactor's auxiliary contact in a motor control circuit?

Monitor motor temperature and trip on overtemperature
Limit inrush current during initial motor energization
Protect the motor against phase loss conditions
Provide a holding circuit to maintain the contactor energized after the start button is released (Correct answer)

Correct answer: Provide a holding circuit to maintain the contactor energized after the start button is released

The normally-open auxiliary (sealing) contact creates a parallel path around the momentary start pushbutton, latching the coil circuit closed after the button is released.

Question 18: Why is hazard prevention crucial in electrical work?

It allows faster installation.
It prevents accidents, injuries, and fatalities during electrical work. (Correct answer)
It reduces the number of components used.
It focuses on the aesthetic appeal of the system.

Correct answer: It prevents accidents, injuries, and fatalities during electrical work.

Hazard prevention is paramount in electrical work due to the inherent dangers associated with electricity, such as high voltage and current. Proactively identifying and mitigating potential hazards, like exposed wires or improper grounding, directly prevents severe accidents, life-threatening injuries, and fatalities. This proactive approach ensures a safer environment for electricians and anyone near electrical installations.

Question 19: How do Legally Required Standby Systems under NEC Article 701 differ from Emergency Systems under Article 700?

They are not subject to periodic testing requirements
They must restore power within 10 seconds like Article 700
They are required by law for specific occupancies but serve loads less critical than Article 700 life-safety loads (Correct answer)
They may supply life-safety loads in place of Article 700 systems

Correct answer: They are required by law for specific occupancies but serve loads less critical than Article 700 life-safety loads

NEC Article 701 covers standby systems mandated by governmental authority for specific occupancies, but serving loads such as heating and industrial processes rather than direct life-safety loads covered by Article 700.

Question 20: What is the maximum voltage drop recommended by NEC 215.2(A)(4) for feeder circuits to optimize energy efficiency?

2%
1%
3% (Correct answer)
5%

Correct answer: 3%

NEC 215.2(A)(4) recommends feeder voltage drop not exceed 3% (with a combined branch and feeder total not exceeding 5%) for energy efficiency.

Question 21: A master electrician receives payment for a project but fails to pay the electrical subcontractors. This behavior:

Is permissible if disclosed to the licensing board
Is acceptable if the client delayed payment first
Violates professional ethics and may constitute grounds for license disciplinary action (Correct answer)
Is a civil matter unrelated to professional licensure

Correct answer: Violates professional ethics and may constitute grounds for license disciplinary action

Financial dishonesty toward subcontractors is an ethical violation that many licensing boards treat as grounds for disciplinary action.

Question 22: Which project management tool is BEST suited for tracking task dependencies and overall project timeline in a visual format?

Work breakdown structure
Gantt chart (Correct answer)
Risk register
Fishbone diagram

Correct answer: Gantt chart

A Gantt chart visually displays project tasks on a timeline, showing start/end dates, durations, and task dependencies in an easy-to-read horizontal bar format.

Question 23: Per NEC 110.26(C)(2), what is the minimum headroom required for electrical equipment rated 1,200A or more that is over 6 ft wide?

7 ft (2.13 m)
6 ft (1.83 m)
6.5 ft (2.0 m) (Correct answer)
8 ft (2.44 m)

Correct answer: 6.5 ft (2.0 m)

NEC 110.26(C)(2) requires a minimum headroom of 6.5 ft for service equipment, switchboards, or panelboards rated 1,200A or more that exceed 6 ft in width.

Question 24: A 480V motor control center is being serviced. The qualified electrician must maintain what minimum distance for the restricted approach boundary?

Restricted boundary = 3 ft 6 in
Restricted boundary = 1 ft 0 in
Avoid contact (1 inch) (Correct answer)
Restricted boundary = 2 ft 2 in

Correct answer: Avoid contact (1 inch)

Per NFPA 70E Table 130.4(D)(a), for 151–750V systems, the restricted approach boundary is 'avoid contact' (essentially 0 inches clearance).

Question 25: Under NFPA 70E, what does the term 'incident energy' refer to in arc flash analysis?

The peak inrush current energy during motor starting
The electrical energy dissipated in a conductor during a ground fault
The total energy stored in a capacitor bank at rated voltage
The amount of thermal energy impressed on a surface at a given distance during an arcing fault (Correct answer)

Correct answer: The amount of thermal energy impressed on a surface at a given distance during an arcing fault

Incident energy is the thermal energy (cal/cm²) that could be released onto a worker's body at a specific distance during an arc flash event.

Question 26: A state electrical licensing law requires continuing education for license renewal. Which body typically administers and enforces this requirement?

OSHA regional office
NFPA
Local AHJ
State electrical licensing board or department (Correct answer)

Correct answer: State electrical licensing board or department

State electrical licensing boards or departments administer continuing education requirements and enforce compliance as a condition of license renewal.

Question 27: Class III hazardous locations are characterized by the presence of:

Flammable gases or vapors
Combustible dust
Ignitable fibers or flyings (Correct answer)
Explosive chemical compounds

Correct answer: Ignitable fibers or flyings

Class III locations are those where ignitable fibers or flyings are present but not likely to be in suspension in sufficient quantities to produce ignitable mixtures.

Question 28: Per NEC 220.87, when determining the existing load on a service being upgraded, the maximum demand data must cover a minimum period of:

14 days
30 days (Correct answer)
60 days
7 days

Correct answer: 30 days

NEC 220.87 requires that maximum demand data be based on a minimum 30-day period to determine existing load.

Question 29: Which device is most effective for mitigating voltage sags caused by motor starting on a distribution system?

Static VAR compensator (SVC) (Correct answer)
Overcurrent relay
Surge arrestor
Ground fault relay

Correct answer: Static VAR compensator (SVC)

A static VAR compensator rapidly injects or absorbs reactive power to stabilize voltage during transient events like motor starting.

Question 30: Under NEC 690.31(B), PV source and output circuit conductors must be identified at:

Each overcurrent device location
All points of termination, connection, and splices (Correct answer)
The inverter terminals only
The main service disconnect only

Correct answer: All points of termination, connection, and splices

NEC 690.31(B) requires DC PV conductors to be identified at all termination, connection, and splice points to prevent dangerous errors during installation and maintenance.

Question 31: An apprentice electrician, working within the scope of their employment for an electrical contracting company, negligently causes damage to a client's server rack. Under the legal doctrine of "respondeat superior," who is typically held liable for the damages?

The client, for not adequately protecting their equipment.
The local electrical inspector who approved the permit.
The master electrician's company (the employer). (Correct answer)
The apprentice only, as they performed the negligent act.

Correct answer: The master electrician's company (the employer).

The doctrine of *respondeat superior* (Latin for "let the master answer") holds an employer legally responsible for the wrongful acts of an employee, provided the acts occur within the scope of employment. Because the apprentice was an employee performing job-related duties, their employer is vicariously liable for the resulting damages.

Question 32: What is the maximum length permitted for a flexible cord used as a listed appliance connection under NEC 400.8, assuming no exception applies?

Flexible cords are prohibited as permanent wiring in all cases (Correct answer)
6 feet
10 feet
25 feet

Correct answer: Flexible cords are prohibited as permanent wiring in all cases

NEC 400.8 prohibits flexible cords from being used as a substitute for permanent wiring; they are permitted only for specific listed uses such as pendants and appliance connections.

Question 33: A supply-side bonding jumper is used to bond metal enclosures on which side of the service or separately derived system?

The load side of all distribution panelboards
Only at grounding electrode connections
The load side of the main service disconnect only
The supply side, between the service or separately derived system source and the first disconnecting means (Correct answer)

Correct answer: The supply side, between the service or separately derived system source and the first disconnecting means

Per NEC 250.102(C), supply-side bonding jumpers bond metal enclosures and raceways on the supply side of the service or between a separately derived system and its first disconnecting means.

Question 34: A 208Y/120V, 3-phase, 4-wire panel serves 30 A of balanced resistive lighting load per phase at 120V. What is the neutral current?

30 A
10 A
0 A (Correct answer)
52 A

Correct answer: 0 A

A perfectly balanced 3-phase, 4-wire wye load produces zero neutral current because the phase currents cancel vectorially.

Question 35: What is the statute of limitations, and why is it critical in construction law?

The maximum project duration allowed under state law
A legal deadline after which claims or lawsuits can no longer be filed (Correct answer)
The warranty period required for electrical installations
The time limit for submitting permit applications

Correct answer: A legal deadline after which claims or lawsuits can no longer be filed

The statute of limitations is a legally mandated time window within which a party must file a lawsuit or legal claim, after which courts will bar the action.

Question 36: NEC 630.11 requires conductors supplying an AC transformer arc welder to have an ampacity of not less than:

100% of rated primary current
70% of rated primary current
125% of rated primary current
50% of rated primary current (Correct answer)

Correct answer: 50% of rated primary current

NEC 630.11(A) sets the minimum conductor ampacity for arc welders at 50% of rated primary current when accounting for duty cycle, as welders do not operate continuously.

Question 37: When using a portable generator on a job site, which safety measure is MOST critical to prevent carbon monoxide poisoning?

Operating it at least 20 feet from building openings (Correct answer)
Connecting it to a GFCI receptacle
Using only 12 AWG extension cords
Installing a transfer switch

Correct answer: Operating it at least 20 feet from building openings

Generators must be kept at least 20 feet from doors, windows, and vents to prevent CO buildup inside structures.

Question 38: What is a compliance audit in CME practice?

A customer satisfaction survey
A systematic review to verify adherence to regulatory requirements and organizational policies (Correct answer)
A financial profit assessment
An employee performance review

Correct answer: A systematic review to verify adherence to regulatory requirements and organizational policies

A compliance audit systematically examines an organization's adherence to external regulations, internal policies, and industry standards, identifying gaps and recommending corrective actions to achieve full compliance.

Question 39: A 3-phase, 4-wire, 208Y/120V panelboard serves a mixed load. Per NEC 408.36, what is the maximum number of overcurrent devices (poles) permitted in a lighting and appliance branch circuit panelboard?

24 poles
No maximum specified
30 poles
42 poles (Correct answer)

Correct answer: 42 poles

NEC 408.36 limits lighting and appliance branch circuit panelboards to a maximum of 42 overcurrent devices (counting each pole of a multi-pole breaker).

Question 40: Per NEC 250.119, equipment grounding conductors must be identified by which of the following?

Orange insulation for systems above 250V
Green insulation, green with yellow stripes, or bare conductor (Correct answer)
White or gray insulation only
Any color except black, red, or blue

Correct answer: Green insulation, green with yellow stripes, or bare conductor

NEC 250.119 requires EGCs to be identified by green insulation, green with yellow stripe insulation, or as a bare conductor to distinguish them from current-carrying conductors.

Question 41: During trench excavation near underground electrical utilities, OSHA requires hand digging or vacuum excavation within what distance of a marked utility?

18 inches
24 inches (Correct answer)
36 inches
12 inches

Correct answer: 24 inches

OSHA and most state dig-safe laws require hand digging or non-mechanical excavation within 24 inches of a marked underground utility.

Question 42: Which provision in most state electrical licensing laws allows a homeowner to perform electrical work on their own residence without a contractor's license?

The de minimis exemption
The residential carve-out provision
The DIY exception under OSHA
The owner-builder or homeowner exemption (Correct answer)

Correct answer: The owner-builder or homeowner exemption

Most states include an owner-builder or homeowner exemption allowing property owners to perform electrical work on their primary residence, subject to permit and inspection requirements.

Question 43: Per NEC 230.95, ground-fault protection of equipment (GFPE) is required for solidly grounded wye services exceeding 150V to ground but not exceeding 600V phase-to-phase when the service disconnect is rated at or above:

600A
800A
1000A (Correct answer)
100A

Correct answer: 1000A

NEC 230.95 requires GFPE for solidly grounded wye services with service disconnecting means rated 1000A or more to protect against high-level arcing ground faults.

Question 44: Per NEC 250.64(B), a grounding electrode conductor of what size or smaller must be protected from physical damage by installation in a raceway or armor?

4 AWG or smaller
6 AWG or smaller (Correct answer)
8 AWG or smaller
10 AWG or smaller

Correct answer: 6 AWG or smaller

NEC 250.64(B) requires that a 6 AWG or smaller copper GEC exposed to physical damage be protected by installing it in rigid metal conduit, IMC, PVC conduit, EMT, or cable armor.

Question 45: NEC 694.66 requires utility-interactive wind electric systems to include:

Anti-islanding protection to prevent energizing the grid during a utility outage (Correct answer)
Only ungrounded output conductors
A minimum 100-ampere output disconnect
A manual disconnect accessible only to utility personnel

Correct answer: Anti-islanding protection to prevent energizing the grid during a utility outage

NEC 694.66 requires anti-islanding protection so that utility-interactive wind systems automatically disconnect from the grid during a utility outage, protecting utility workers.

Question 46: What is the primary function of the equipment grounding conductor (EGC) in a branch circuit?

To reduce electromagnetic interference in the wiring system
To provide a low-impedance fault current path that enables overcurrent device operation (Correct answer)
To carry normal load current back to the neutral bus
To equalize voltage between ungrounded phase conductors

Correct answer: To provide a low-impedance fault current path that enables overcurrent device operation

The EGC provides a low-impedance path for fault current to return to the source, ensuring sufficient current flows to operate the overcurrent protective device and clear the fault.

Question 47: What is the function of a conduit seal (sealing fitting) installed in a hazardous location per NEC 501.15?

Prevent flame or explosion from propagating through the conduit system between hazardous and non-hazardous areas (Correct answer)
Reduce harmonic distortion on branch circuits in industrial settings
Prevent moisture from entering electrical enclosures in wet locations
Maintain pressure within explosion-proof enclosures during fault events

Correct answer: Prevent flame or explosion from propagating through the conduit system between hazardous and non-hazardous areas

Conduit seals filled with approved compound prevent ignited gases inside an enclosure from traveling through the conduit and igniting gases in adjacent areas.

Question 48: During a project, a foreman discovers a conflict between the architectural drawings and the electrical plans, making the specified installation impossible. What is the proper document the master electrician should issue to the general contractor to formally request clarification and receive a documented response?

A Request for Information (RFI). (Correct answer)
A Change Order Request.
A Submittal Package.
A Field Directive.

Correct answer: A Request for Information (RFI).

A Request for Information (RFI) is the standard, formal document used in construction to ask for clarification of plans, drawings, specifications, or agreements. It creates a documented record of the question and the official answer, which is crucial for liability and potential changes. A Change Order is for altering the contract, a Submittal is for product approval, and a Field Directive is an instruction from the architect or owner.

Question 49: Which NEC article covers the electrical installation requirements for industrial machinery?

NEC Article 670 (Correct answer)
NEC Article 409
NEC Article 440
NEC Article 430

Correct answer: NEC Article 670

NEC Article 670 covers industrial machinery, defining supply conductor sizing, disconnecting means, and overcurrent protection for machine tools and similar equipment.

Question 50: Per NEC 220.87, what is the permitted method for determining the existing load on a service for the purpose of adding new loads?

Calculate 80% of the service rating
Use actual maximum demand data for a 1-year period (Correct answer)
Measure peak demand over any 30-day period and multiply by 1.25
Calculate connected load using NEC demand factors

Correct answer: Use actual maximum demand data for a 1-year period

NEC 220.87 permits using actual maximum demand data recorded over a minimum 1-year period to determine the existing load for service upgrade calculations.

Question 51: Which PPE category under NFPA 70E requires arc-rated clothing with a minimum arc rating of 40 cal/cm²?

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

Correct answer: Category 4

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

Question 52: Which NEC article governs the design and installation requirements for emergency systems in commercial buildings?

Article 702
Article 700 (Correct answer)
Article 708
Article 701

Correct answer: Article 700

NEC Article 700 covers emergency systems that are legally required and essential for safety to human life.

Question 53: When installing an equipotential plane in a concrete floor area of an agricultural building where livestock are confined, which of the following is a key requirement according to NEC 547.10?

The equipotential plane must be connected only to a separate, dedicated grounding rod.
The plane must be made of non-conductive materials to isolate the livestock.
The equipotential plane is only required if the building has a metal frame.
The plane must be connected to the electrical grounding system with a copper conductor, not smaller than 8 AWG. (Correct answer)

Correct answer: The plane must be connected to the electrical grounding system with a copper conductor, not smaller than 8 AWG.

NEC 547.10(C) requires the equipotential plane to be bonded to the building's electrical grounding system. The bonding conductor must be copper (insulated, covered, or bare) and not smaller than 8 AWG. This practice helps to reduce voltage gradients (stray voltage) across the concrete surface, which can be harmful to livestock.

Question 54: Which class of fire extinguisher is appropriate for energized electrical equipment fires?

Class A
Class C (Correct answer)
Class B
Class D

Correct answer: Class C

Class C extinguishers use non-conductive agents suitable for energized electrical equipment fires.

Question 55: Under NEC Article 110.26, what is the minimum working space depth in front of a 480V panelboard with exposed live parts on both sides?

3 feet
5 feet
4 feet (Correct answer)
2 feet

Correct answer: 4 feet

Condition 3 (live parts on both sides) at 151–600V requires a minimum working space depth of 4 feet per NEC 110.26.

Question 56: What is the minimum conductor insulation temperature rating required when conductors are connected to a 75°C-rated terminal on a circuit breaker?

90°C
75°C (Correct answer)
110°C
60°C

Correct answer: 75°C

The conductor insulation must be rated at least equal to the terminal rating, so a 75°C terminal requires at minimum a 75°C-rated conductor.

Question 57: Which grounding electrode has the highest priority in the grounding electrode system hierarchy per NEC 250.50?

Metal underground water pipe with 10+ feet in contact with soil (Correct answer)
Ground rod driven 8 feet into earth
Concrete-encased electrode
Plate electrode

Correct answer: Metal underground water pipe with 10+ feet in contact with soil

NEC 250.52(A)(1) lists the metal underground water pipe as the first electrode in the hierarchy, and NEC 250.50 requires it to be used if present, supplemented by additional electrodes.

Question 58: Per NEC 240.4(D), what is the maximum overcurrent protection permitted for a 12 AWG copper branch-circuit conductor?

25A
15A
20A (Correct answer)
30A

Correct answer: 20A

NEC 240.4(D)(5) limits overcurrent protection for 12 AWG copper conductors to a maximum of 20A.

Question 59: A motor repeatedly trips its overload relay shortly after reset. The motor is running at rated load. What is the MOST likely cause?

High ambient temperature around the motor
Oversized overload relay heater elements
Undersized supply conductors causing voltage drop (Correct answer)
Defective overload relay contact block

Correct answer: Undersized supply conductors causing voltage drop

Undersized supply conductors cause voltage drop, which increases motor current draw and causes repeated overload trips under rated load conditions.

Question 60: Which signal word on a product label indicates the MOST severe hazard level under GHS/HazCom?

Notice
Caution
Danger (Correct answer)
Warning

Correct answer: Danger

'Danger' is the GHS signal word for severe hazards, while 'Warning' is used for less severe hazards.

Question 61: In designing a motor control center (MCC) for an industrial plant, what is the minimum short-circuit current rating (SCCR) that must be marked on the MCC assembly per NEC 409.110?

42,000A for all 480V industrial installations
5,000A minimum unless labeled for specific ampere rating (Correct answer)
10,000A minimum for all industrial MCCs
The SCCR must equal the available fault current at the installation point

Correct answer: 5,000A minimum unless labeled for specific ampere rating

NEC 409.110(4) requires industrial control panels to be marked with their SCCR, with a minimum of 5,000A unless the panel is marked for a specific higher rating.

Question 62: A master electrician notices that a previous contractor's wiring is code-compliant under an older adopted edition but unsafe by current standards. The BEST course of action is to:

File a complaint against the previous contractor only
Immediately rewire without the owner's knowledge
Ignore it since it passed inspection under the old code
Inform the owner of the risk and recommend upgrading to current standards (Correct answer)

Correct answer: Inform the owner of the risk and recommend upgrading to current standards

Informing the owner of the risk respects their autonomy while fulfilling the master electrician's professional duty to disclose hazards.

Question 63: Under NEC Article 517, the critical branch of a hospital's essential electrical system must restore power within how many seconds of interruption?

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

Correct answer: 10 seconds

NEC 517.31(B) requires the critical branch to be restored within 10 seconds, as it serves life-safety loads such as critical care areas and task illumination.

Question 64: Which federal law requires employers to record and report work-related injuries and illnesses, affecting electrical contractors' safety documentation?

The National Electrical Safety Code (NESC)
The Fair Labor Standards Act (FLSA)
The Occupational Safety and Health Act (OSH Act) (Correct answer)
The National Labor Relations Act (NLRA)

Correct answer: The Occupational Safety and Health Act (OSH Act)

The OSH Act requires covered employers to maintain OSHA 300 logs and report serious work-related injuries and fatalities to OSHA.

Question 65: Which OSHA standard specifically governs electrical safety requirements for general industry (not construction)?

29 CFR 1926 Subpart K
29 CFR 1910 Subpart J
29 CFR 1910 Subpart S (Correct answer)
29 CFR 1926 Subpart V

Correct answer: 29 CFR 1910 Subpart S

29 CFR 1910 Subpart S covers electrical safety standards for general industry workplaces.

Question 66: A subcontractor on your electrical project files a mechanic's lien. What is the primary purpose of this lien?

To transfer ownership of the project
To void the general contractor's license
To secure payment for labor and materials provided (Correct answer)
To delay project completion legally

Correct answer: To secure payment for labor and materials provided

A mechanic's lien gives unpaid contractors or suppliers a legal claim against the property to secure compensation for their work or materials.

Question 67: Per NEC Table 250.66, what is the minimum size copper grounding electrode conductor (GEC) for a service with 3/0 AWG copper service-entrance conductors?

1/0 AWG
2/0 AWG
4 AWG (Correct answer)
2 AWG

Correct answer: 4 AWG

NEC Table 250.66 requires a 4 AWG copper GEC when the largest service-entrance conductor is 3/0 AWG copper.

Question 68: NEC 525.20 requires flexible cords and cables used for electrical equipment at carnivals and circuses to be rated for:

Extra-hard usage (Type SOOW or equivalent) (Correct answer)
Indoor use only (Type SJO)
Hard usage (Type SO)
Portable use only (Type SPT)

Correct answer: Extra-hard usage (Type SOOW or equivalent)

NEC 525.20(A) requires carnival and circus flexible cords to be listed for extra-hard usage due to the physical abuse they are subjected to in outdoor traveling environments.

Question 69: A facility operates 500 kW of load for 12 hours at night and 1,200 kW for 12 hours during the day. What is the daily load factor?

0.500
0.708 (Correct answer)
0.833
0.417

Correct answer: 0.708

Load factor = average demand / peak demand = [(500×12 + 1200×12)/24] / 1200 = 850/1200 ≈ 0.708.

Question 70: A concrete-encased electrode (Ufer ground) must contain at least how many feet of bare copper conductor or steel rebar per NEC 250.52(A)(3)?

15 feet
20 feet (Correct answer)
25 feet
10 feet

Correct answer: 20 feet

NEC 250.52(A)(3) requires at least 20 feet of bare copper conductor (4 AWG or larger) or 20 feet of steel rebar (½ inch or larger) encased in concrete for a concrete-encased electrode.

Question 71: Under OSHA 29 CFR 1926 Subpart K, which of the following is required before performing electrical work on construction sites?

Lockout/tagout procedures and de-energization where feasible (Correct answer)
A permit from the NEC
Written approval from the project architect
An Energized Work Permit per NFPA 70

Correct answer: Lockout/tagout procedures and de-energization where feasible

OSHA 29 CFR 1926 Subpart K requires that electrical equipment be de-energized and controlled through lockout/tagout before work, unless infeasible.

Question 72: What does a displacement power factor of 0.95 lagging indicate about a facility's electrical load?

The load has significant harmonic distortion offsetting true power factor
The load is purely resistive with no reactive component
The load is predominantly inductive, drawing reactive power from the utility (Correct answer)
The load is capacitive and supplying reactive power to the grid

Correct answer: The load is predominantly inductive, drawing reactive power from the utility

A lagging displacement power factor indicates inductive loads (motors, transformers) consuming reactive power, which increases apparent power demand.

Question 73: A feeder supplies power to three continuous-duty motors with full-load currents of 40A, 30A, and 25A, and a non-continuous, non-motor load of 50A. What is the minimum required ampacity for the feeder conductors?

155A
165A (Correct answer)
181.25A
145A

Correct answer: 165A

According to NEC 430.24, the feeder ampacity must be calculated by taking 125% of the largest motor's full-load current (FLC), and adding the sum of the FLCs of the remaining motors and other loads. For feeders supplying both motor and non-motor loads, the calculation is: (1.25 × FLC of largest motor) + (Sum of FLC of all other motors) + (1.25 x Continuous non-motor load) + (100% x Non-continuous non-motor load). In this scenario: (1.25 × 40A) + 30A + 25A + 50A = 50A + 30A + 25A + 50A = 155A.

Question 74: When a grounding electrode conductor is run inside a ferrous metal raceway, what bonding requirement applies per NEC 250.64(E)?

The raceway must be bonded at one end only to prevent circulating currents
The raceway must be bonded to the GEC at both ends to prevent inductive choke effect (Correct answer)
No special bonding is required for GEC raceways
The raceway must be removed and replaced with non-metallic conduit

Correct answer: The raceway must be bonded to the GEC at both ends to prevent inductive choke effect

NEC 250.64(E) requires ferrous metal raceways enclosing GECs to be bonded to the GEC at both ends to prevent inductive heating and voltage drop caused by the raceway acting as a choke.

Question 75: Under the NEC Article 505 Zone system, equipment used in a Zone 0 location must be classified as:

Category 1 (Correct answer)
Category 3
Zone-rated only
Category 2

Correct answer: Category 1

Zone 0, where explosive atmospheres are continuously present, requires Category 1 equipment providing the highest protection level for continuous ignition risk.

Question 76: NEC 700.4 requires emergency systems to be tested at intervals not exceeding:

12 months
6 months
30 days (Correct answer)
90 days

Correct answer: 30 days

NEC 700.4(B) requires emergency systems to be tested at least every 30 days to ensure reliable operation during life-safety emergencies.

Question 77: When conductors are installed in parallel in multiple raceways, how must equipment grounding conductors be installed per NEC 250.122(F)?

Only required in raceways containing the largest conductor
Not required if metallic raceways serve as the EGC
In each raceway, each sized per Table 250.122 based on the overcurrent device (Correct answer)
In only one raceway, sized for total combined load

Correct answer: In each raceway, each sized per Table 250.122 based on the overcurrent device

NEC 250.122(F) requires an EGC to be installed in each raceway when parallel conductors are used, with each EGC sized per Table 250.122 for the circuit overcurrent device.

Question 78: An electrician is replacing a single-phase, 240-volt pool filter motor at a residential dwelling. According to NEC Article 680, what is the primary requirement for the branch circuit supplying this motor?

It must be supplied from a dedicated transformer.
It must be hard-wired using Type MC cable.
It must be protected by a ground-fault circuit-interrupter (GFCI). (Correct answer)
It must have short-circuit and ground-fault protection not exceeding 125% of the motor FLC.

Correct answer: It must be protected by a ground-fault circuit-interrupter (GFCI).

NEC 680.21(C) mandates that outlets supplying pool pump motors connected to single-phase, 120-volt through 240-volt branch circuits must be provided with Class A ground-fault circuit-interrupter protection for personnel, whether supplied by a receptacle or by direct connection.

Question 79: Under NEC 225.30, what is the maximum number of branch circuits or feeders permitted to supply a separate building from a single source?

Four
Two
Six
One (Correct answer)

Correct answer: One

NEC 225.30 generally limits the supply to a separate building to one feeder or branch circuit, with specific exceptions.

Question 80: Under NEC Article 640, audio distribution cables installed in a plenum space must be:

Rated for 300V minimum insulation
Limited to runs under 25 feet without conduit
Listed for plenum use such as CL2P or CL3P (Correct answer)
Enclosed in metal conduit for any length

Correct answer: Listed for plenum use such as CL2P or CL3P

NEC 640.9(C) requires cables in plenum spaces to be listed for plenum use (CL2P or CL3P) due to reduced smoke and flame propagation characteristics required in air-handling spaces.

Question 81: Under NEC 110.26(A)(1), the minimum clear working space in front of electrical equipment operating at 120/240 volts to ground, with exposed live parts on one side and grounded parts on the other (Condition 2), is how many feet?

4 feet
3.5 feet (Correct answer)
6 feet
3 feet

Correct answer: 3.5 feet

NEC Table 110.26(A)(1) specifies 3.5 feet of working clearance for Condition 2 at voltages of 151–600 volts; for 0–150 volts Condition 2 it is 3 feet.

Question 82: A 20-unit multifamily dwelling is being calculated using the optional method per NEC 220.84. Each unit contains 1,200 sq ft of living space, two small-appliance circuits, one laundry circuit, a 12 kW range, a 5 kW water heater, and a 4.5 kW dryer. What is the total connected load for one unit before applying the demand factor from Table 220.84?

31,100 VA
25,100 VA
35,600 VA (Correct answer)
29,600 VA

Correct answer: 35,600 VA

Per NEC 220.84(C), the total connected load is the sum of various loads. The calculation for one unit is: General Lighting (1,200 sq ft × 3 VA/sq ft) = 3,600 VA. Small-Appliance Circuits (2 circuits × 1,500 VA) = 3,000 VA. Laundry Circuit (1 circuit × 1,500 VA) = 1,500 VA. Range (nameplate) = 12,000 VA. Water Heater (nameplate) = 5,000 VA. Dryer (nameplate) = 4,500 VA. Air Conditioning (larger than heat) = 6,000 VA. Total Connected Load = 3,600 + 3,000 + 1,500 + 12,000 + 5,000 + 4,500 + 6,000 = 35,600 VA.

Question 83: Per NEC 645.10, the disconnecting means required in an information technology equipment room must disconnect:

All IT equipment power and dedicated HVAC systems serving the room (Correct answer)
The room's lighting circuits only
Branch circuits to individual server racks
Only equipment rated over 20 amperes

Correct answer: All IT equipment power and dedicated HVAC systems serving the room

NEC 645.10 requires a single disconnecting means capable of de-energizing all electronic equipment in the IT room and HVAC systems dedicated to that room for emergency shutdown.

Question 84: A branch circuit shows correct voltage at the panel but low voltage at the last receptacle in a long run. No load is connected. What does this indicate?

An undersized circuit breaker limiting current flow
A high-resistance splice or connection in the circuit (Correct answer)
Normal voltage variation within NEC tolerance
Excessive voltage drop due to conductor resistance under load

Correct answer: A high-resistance splice or connection in the circuit

Voltage drop with no connected load indicates a high-resistance connection (loose splice, corroded terminal) rather than conductor size, since resistive drop under no-load should be negligible.

Question 85: A three-phase 480V motor is humming loudly and not starting. A voltmeter check shows 480V across two phases but zero volts on the third. What is the likely problem?

One phase of the supply is open (single-phasing) (Correct answer)
The overload relay has tripped
The motor bearings have seized
The motor windings are shorted

Correct answer: One phase of the supply is open (single-phasing)

Zero volts on one phase while the other two phases read correctly indicates an open phase (single-phasing), which prevents the motor from starting and causes the characteristic loud hum.

Question 86: In an electrical system design using a separately derived system (480-208Y/120V transformer), where must the system bonding jumper be installed per NEC 250.30(A)(1)?

At the first downstream distribution panel only
At the transformer or at the first disconnecting means (Correct answer)
At every panel served by the transformer
At the utility service entrance

Correct answer: At the transformer or at the first disconnecting means

NEC 250.30(A)(1) requires the system bonding jumper for a separately derived system to be installed at the source (transformer) or at the first disconnecting means, but not both.

Question 87: A master electrician is offered a gift by a material supplier in exchange for specifying their products exclusively. Accepting this gift is considered:

A conflict of interest that compromises professional objectivity (Correct answer)
Acceptable if disclosed to the employer
Standard industry practice
Permitted as long as the product meets code

Correct answer: A conflict of interest that compromises professional objectivity

Accepting gifts in exchange for specification decisions creates a conflict of interest and undermines the electrician's professional independence.

Question 88: What is the purpose of electrical system grounding?

To increase the system’s efficiency.
To ensure safe discharge of faults and prevent electrical shock. (Correct answer)
To increase the system’s power output.
To reduce the system’s wiring complexity.

Correct answer: To ensure safe discharge of faults and prevent electrical shock.

Electrical system grounding is a fundamental safety measure designed to provide a safe path for fault currents to dissipate into the earth. In the event of an electrical fault, grounding prevents dangerous voltage buildup on conductive surfaces, which could otherwise cause severe electric shocks. It also helps circuit breakers and fuses trip quickly, protecting equipment and personnel.

Question 89: Under NEC Article 210, what is the maximum distance from a doorway that a receptacle outlet must be placed in a dwelling unit wall space?

4 feet
12 feet
6 feet (Correct answer)
8 feet

Correct answer: 6 feet

NEC 210.52(A) requires receptacles within 6 feet of any doorway opening in dwelling unit wall spaces.

Question 90: Under NEC 210.8, GFCI protection is required for all 15A and 20A, 125V receptacles in which residential location?

Living rooms only if within 6 feet of a water source
Home offices with dedicated circuits
All unfinished basement areas (Correct answer)
Bedrooms in homes built before 1990

Correct answer: All unfinished basement areas

NEC 210.8(A)(5) requires GFCI protection for all 125V, 15 and 20A receptacles in unfinished basement areas of dwelling units.

Question 91: Which organization sets national electrical codes in the United States?

Occupational Safety and Health Administration (OSHA).
National Fire Protection Association (NFPA). (Correct answer)
U.S. Environmental Protection Agency (EPA).
Federal Communications Commission (FCC).

Correct answer: National Fire Protection Association (NFPA).

The National Fire Protection Association (NFPA) is the organization responsible for developing and publishing the National Electrical Code (NEC) in the United States. The NEC is a widely adopted standard that provides comprehensive requirements for safe electrical installations. While other organizations have roles in electrical safety, NFPA is the specific body for the NEC.

Question 92: Per NEC 110.9, equipment used to interrupt fault current must have an interrupting rating that is:

At least equal to the maximum available fault current at its terminals (Correct answer)
Rated for 10,000 AIC minimum regardless of system fault levels
Determined only by the utility company
Based solely on the conductor ampacity

Correct answer: At least equal to the maximum available fault current at its terminals

NEC 110.9 requires that equipment intended to interrupt current at fault levels must have an interrupting rating sufficient for the available fault current at its terminals.

Question 93: Per NEC 250.70, connections of grounding electrode conductors to grounding electrodes must be made using:

Listed lugs, listed pressure connectors, listed clamps, or other listed means approved for the purpose (Correct answer)
Wire nuts rated for outdoor use
Mechanical set-screw connectors only
Any UL-listed wire connector rated for the conductor size

Correct answer: Listed lugs, listed pressure connectors, listed clamps, or other listed means approved for the purpose

NEC 250.70 requires that connections of GECs to grounding electrodes use listed lugs, listed pressure connectors, listed clamps, or other listed means approved for the material and electrode type.

Question 94: A dwelling unit has a 5 kW, 240V dishwasher and a 1.5 kW, 120V garbage disposal. What is the combined demand load using the NEC standard calculation method?

Both must be included at full nameplate rating (Correct answer)
6,500 VA at 100%
6,500 VA
6,500 W

Correct answer: Both must be included at full nameplate rating

Per NEC 220.53, household appliances are subject to 75% demand when four or more are present; with only two appliances, both are counted at 100% of nameplate rating.

Question 95: Per NEC 250.53(A)(2), when is a supplemental grounding electrode required when a single rod, pipe, or plate electrode is used?

Always, regardless of soil resistance
When the electrode is longer than 8 feet
When the single electrode has a resistance to ground exceeding 25 ohms (Correct answer)
When the service exceeds 200A

Correct answer: When the single electrode has a resistance to ground exceeding 25 ohms

NEC 250.53(A)(2) requires a supplemental electrode when a single rod, pipe, or plate electrode has a resistance to ground exceeding 25 ohms.

Question 96: Per NEC Article 250, what is the primary purpose of bonding metal parts in an electrical system?

To increase the current-carrying capacity of conductors
To reduce voltage drop in branch circuits
To provide surge protection from lightning
To establish electrical continuity and conductivity between metal parts (Correct answer)

Correct answer: To establish electrical continuity and conductivity between metal parts

Bonding establishes electrical continuity and conductivity between conductive parts to ensure a reliable fault current path and equalize potential differences.

Question 97: Under NEC 250.66, the size of the grounding electrode conductor for a copper service entrance conductor sized at 2/0 AWG is determined by which table?

Table 250.66 (Correct answer)
Table 250.122
Table 310.15(B)(16)
Table 310.16

Correct answer: Table 250.66

NEC Table 250.66 is used to determine the minimum size of the grounding electrode conductor based on the largest service-entrance conductor.

Question 98: In CME practice, what is a corrective action plan?

A plan to correct employee behavior problems
A plan for office renovations
A documented strategy to address identified compliance deficiencies and prevent recurrence (Correct answer)
A strategy to increase sales

Correct answer: A documented strategy to address identified compliance deficiencies and prevent recurrence

A corrective action plan outlines specific steps to address identified compliance violations or deficiencies, including root cause analysis, remediation activities, responsible parties, timelines, and measures to prevent recurrence.

Question 99: The main bonding jumper at a service connects which two components?

The grounding electrode conductor to the service entrance conduit
The grounded (neutral) conductor to the equipment grounding conductor at the main service (Correct answer)
The neutral bar to the grounding electrode only
The hot conductor to the neutral conductor at the panel

Correct answer: The grounded (neutral) conductor to the equipment grounding conductor at the main service

Per NEC 250.28, the main bonding jumper connects the grounded (neutral) conductor to the equipment grounding conductor and enclosure at the main service disconnect.

Question 100: What NEC article covers the installation requirements for generators?

Article 445 (Correct answer)
Article 702
Article 430
Article 700

Correct answer: Article 445

NEC Article 445 specifically addresses generators, including their overcurrent protection and conductor sizing.

Certified Master Electrician (CME) Exam

The Certified Master Electrician exam tests comprehensive knowledge of the National Electrical Code (NEC), electrical theory, wiring methods, load calculations, and advanced electrical systems required for master-level licensure.

100

Questions

300 min

Time Limit

75%

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