Certified Master Electrician (CME) Exam — Questions and Answers

Question 1: Under OSHA 1910.137, insulated rubber gloves must be electrically tested at intervals not exceeding how many months?

24 months
6 months (Correct answer)
12 months
3 months

Correct answer: 6 months

OSHA 1910.137 requires rubber insulating gloves to be tested every 6 months to ensure dielectric integrity.

Question 2: NEC Article 708 Critical Operations Power Systems (COPS) apply to facilities that:

Have more than 1,000 occupants
Contain medical imaging equipment
Exceed 50,000 square feet of floor area
Protect national security, emergency communications, or continuity of government (Correct answer)

Correct answer: Protect national security, emergency communications, or continuity of government

NEC Article 708 applies to facilities designated as critical operations power systems where loss of power could disrupt national security, public safety communications, or government continuity.

Question 3: What does a high resistance reading across a closed switch or contactor contact indicate?

The switch has adequate interrupting capacity
The insulation is beginning to break down
The contacts are burned, pitted, or contaminated (Correct answer)
The switch rating exceeds circuit requirements

Correct answer: The contacts are burned, pitted, or contaminated

High resistance across closed contacts indicates burned, pitted, or contaminated contact surfaces that impede current flow and cause voltage drop and heat.

Question 4: Per NEC 625.41, EV charging equipment (EVSE) must be rated at not less than what percentage of the maximum load?

100%
125% (Correct answer)
115%
150%

Correct answer: 125%

NEC 625.41 requires EVSE to be rated at not less than 125% of the maximum load because EV charging is treated as a continuous load.

Question 5: In a switchboard installation, what is the minimum headroom required in front of the equipment per NEC 110.26(A)(3)?

5.5 feet
6.5 feet (Correct answer)
6 feet
7 feet

Correct answer: 6.5 feet

NEC 110.26(A)(3) requires a minimum headroom of 6.5 feet (2.0 m) in front of electrical equipment 600V or less.

Question 6: Why is energy efficiency important in electrical systems design?

To increase the system's energy consumption.
To reduce operational costs and minimize environmental impact. (Correct answer)
To increase the cost of operation.
To focus only on short-term profits.

Correct answer: To reduce operational costs and minimize environmental impact.

Energy efficiency in electrical systems design focuses on minimizing wasted energy, which directly translates to lower electricity bills and reduced operational costs over the system's lifespan. Furthermore, by consuming less energy, the system contributes to a smaller carbon footprint and reduced demand on power generation, thereby minimizing environmental impact. It's a key aspect of sustainable and cost-effective design.

Question 7: Which organization sets national electrical codes in the United States?

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

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 8: A project owner withholds 10% of each progress payment as 'retainage.' When is this money typically released?

At the end of each calendar quarter
At the midpoint of the project
When 50% of the contract value has been billed
Upon substantial completion and resolution of all punch list items (Correct answer)

Correct answer: Upon substantial completion and resolution of all punch list items

Retainage is typically released after substantial completion, final inspection approval, and resolution of all punch list items, ensuring the contractor finishes all work properly.

Question 9: When conductors are installed in parallel in multiple raceways, how must equipment grounding conductors be installed per NEC 250.122(F)?

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

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 10: 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?

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

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

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

Correct answer: Article 700

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

Question 12: A 120V circuit breaker trips repeatedly under normal load. Beyond the circuit fault, what hidden safety hazard should the electrician inspect for?

Loose or corroded connections causing resistive heating (Correct answer)
Undersized grounding conductor
Incorrect wire color coding
Missing AFCI protection

Correct answer: Loose or corroded connections causing resistive heating

Loose or corroded connections increase resistance, causing resistive heating that can ignite insulation and surrounding materials.

Question 13: What is the primary function of a motor overload relay in a motor branch circuit?

Provide short-circuit protection for the branch circuit conductors
Limit inrush current during motor starting
Disconnect the motor during ground faults
Protect the motor windings from sustained overcurrent due to overloading or locked rotor (Correct answer)

Correct answer: Protect the motor windings from sustained overcurrent due to overloading or locked rotor

Overload relays sense running overcurrent (typically 105–125% FLA) and trip the contactor before the motor's thermal limits are exceeded.

Question 14: Per NEC 240.4(D)(3), what is the maximum overcurrent protection permitted for a 10 AWG copper branch-circuit conductor?

25A
20A
35A
30A (Correct answer)

Correct answer: 30A

NEC 240.4(D)(3) limits overcurrent protection for 10 AWG copper conductors to a maximum of 30A in branch circuits.

Question 15: What is the importance of using a multimeter in troubleshooting electrical systems?

It increases the cost of repairs.
It helps measure voltage, current, and resistance for diagnosing electrical problems. (Correct answer)
It reduces the number of tools needed.
It speeds up the installation process.

Correct answer: It helps measure voltage, current, and resistance for diagnosing electrical problems.

A multimeter is an indispensable tool in electrical troubleshooting because it allows technicians to accurately measure key electrical parameters. It can determine voltage (potential difference), current (flow of electrons), and resistance (opposition to current flow). These measurements are crucial for diagnosing a wide range of electrical problems, such as open circuits, short circuits, and faulty components, enabling precise and effective repairs.

Question 16: Per NEC 240.4(D), what is the maximum overcurrent protection permitted for a 12 AWG copper branch-circuit conductor?

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

Correct answer: 20A

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

Question 17: A master electrician is designing a switchboard installation. Per NEC 408.18, what is the minimum headroom required in front of a switchboard?

6 feet
8 feet
7 feet
6.5 feet (Correct answer)

Correct answer: 6.5 feet

NEC 408.18(A) requires a minimum headroom of 6.5 feet in front of switchboards.

Question 18: Why is it essential to stay updated with changes in electrical codes and standards?

It reduces the need for inspections.
To ensure compliance with current safety and technological standards, minimizing risks. (Correct answer)
It is not important as long as the system is functioning.
It makes electrical systems more expensive.

Correct answer: To ensure compliance with current safety and technological standards, minimizing risks.

Electrical codes and standards are regularly updated to reflect advancements in technology, new safety research, and evolving best practices. Staying updated ensures that electrical systems are designed and installed using the most current and safest methods, reducing the risk of accidents and failures. It also guarantees legal compliance and the long-term reliability of installations.

Question 19: In a Class II, Division 1 location involving combustible dust, what type of enclosure is required for electrical equipment?

Explosionproof
Dust-ignitionproof (Correct answer)
Rainproof
Weatherproof

Correct answer: Dust-ignitionproof

Class II locations involve combustible dust hazards, requiring dust-ignitionproof enclosures that prevent dust entry and any internal arcing from igniting surrounding dust.

Question 20: Which entity has the legal authority to grant a variance from a specific NEC requirement when strict compliance is impractical?

The Authority Having Jurisdiction (AHJ) (Correct answer)
NFPA technical committee
OSHA national office
The state governor's office

Correct answer: The Authority Having Jurisdiction (AHJ)

The AHJ has authority under NEC Section 90.4 to grant variances or equivalencies when strict compliance is impractical, provided equivalent safety is achieved.

Question 21: 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 service exceeds 200A
When the electrode is longer than 8 feet
When the single electrode has a resistance to ground exceeding 25 ohms (Correct answer)

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 22: When installing parallel conductors for a 1200A feeder, what is the minimum conductor size permitted for paralleling per NEC 310.10(H)?

#3/0 AWG
#1 AWG
#1/0 AWG (Correct answer)
#2/0 AWG

Correct answer: #1/0 AWG

NEC 310.10(H)(1) requires that conductors intended for parallel operation be 1/0 AWG or larger.

Question 23: NEC 680.26 requires equipotential bonding for all metal parts within what distance of the inside walls of a swimming pool?

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

Correct answer: 5 feet

NEC 680.26(B) requires all metal parts within 5 feet of the inside walls of a pool to be bonded together to eliminate dangerous voltage differences.

Question 24: What is the primary purpose of an Assured Equipment Grounding Conductor Program (AEGCP) on a construction site?

Document all equipment serial numbers
Replace GFCI protection requirements entirely
Provide an alternative to GFCI by using a systematic inspection and testing program (Correct answer)
Ensure all tools are double-insulated

Correct answer: Provide an alternative to GFCI by using a systematic inspection and testing program

An AEGCP is an OSHA-accepted alternative to GFCI protection that uses systematic inspection and testing of equipment grounding conductors.

Question 25: An electrician is working in a confined space with potential atmospheric hazards. Which gas is considered the most common cause of fatalities in confined spaces?

Hydrogen sulfide
Methane
Oxygen deficiency (Correct answer)
Carbon dioxide

Correct answer: Oxygen deficiency

Oxygen deficiency (below 19.5%) is the leading cause of confined space fatalities because it rapidly incapacitates workers.

Question 26: Under NEC 225.30, what is the maximum number of branch circuits or feeders permitted to supply a separate building from a single source?

Six
Two
One (Correct answer)
Four

Correct answer: One

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

Question 27: For floating buildings under NEC Article 553, where must the disconnecting means for the feeder or service be located?

On the utility pole
At the main shore panel only
Within 50 feet of the water's edge
On the floating building, at the point conductors enter (Correct answer)

Correct answer: On the floating building, at the point conductors enter

NEC 553.4 requires the disconnecting means to be located on the floating building at or near the point where the conductors enter, ensuring accessible isolation.

Question 28: NEC 694.66 requires utility-interactive wind electric systems to include:

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

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

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

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 30: Under NEC 422.31(B), an appliance rated over 300 volt-amperes or 1/8 horsepower must have a disconnecting means within sight OR the disconnecting means can be out of sight if it is what?

Lockable in the open position (Correct answer)
Installed in the same room
Rated at least 200% of the appliance rating
A circuit breaker handle-tied to the neutral

Correct answer: Lockable in the open position

NEC 422.31(B) allows the disconnecting means to be out of sight of the appliance only if it is capable of being locked in the open (off) position.

Question 31: What is the required working space headroom above the finished floor or platform for electrical equipment rated over 600V?

6.0 feet (Correct answer)
5.5 feet
6.5 feet
5.0 feet

Correct answer: 6.0 feet

NEC 110.34 requires a minimum headroom of 6.0 feet for electrical equipment rated over 600V.

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.

Questions

40 min

Time Limit

75%

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