Certified Master Electrician (CME) Exam — Questions and Answers

Question 1: What NEC article covers the installation requirements for generators?

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

Correct answer: Article 445

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

Question 2: For a 240V, 1-phase, 10 kW fixed electric space heater, what is the minimum circuit ampacity required per NEC 424.3(B)?

62.5 A
41.67 A
52.08 A (Correct answer)
50 A

Correct answer: 52.08 A

Fixed electric space heaters are considered continuous loads; 10,000 W / 240 V = 41.67 A × 125% = 52.08 A minimum ampacity.

Question 3: When designing a raceway system through a fire-rated wall, what is required at each penetration per NEC 300.21?

Metallic conduit only may be used through fire walls
The opening must be fire-stopped to maintain the fire rating (Correct answer)
A pull box must be installed within 18 inches of the penetration
A conduit seal fitting must be installed

Correct answer: The opening must be fire-stopped to maintain the fire rating

NEC 300.21 requires that penetrations through fire-resistant-rated walls, floors, and ceilings be firestopped using approved methods to maintain the fire resistance rating.

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

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

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 5: A power factor correction capacitor bank installation causes nuisance tripping of upstream breakers at energization. What is the MOST likely cause?

Harmonic resonance is causing sustained overcurrent
The capacitors are undersized for the connected load
High inrush current during capacitor energization exceeds instantaneous trip setting (Correct answer)
The breakers have insufficient interrupting capacity for the capacitor bank

Correct answer: High inrush current during capacitor energization exceeds instantaneous trip setting

Capacitor banks draw a high inrush current spike at the moment of energization; if the upstream breakers have a low instantaneous trip setting, this momentary spike trips the breaker even though steady-state current is within rating.

Question 6: An electric heating element resistance measured with an ohmmeter reads infinity (open). The element visually shows no breaks. What is the MOST likely explanation?

The element resistance is too low for the ohmmeter range selected
An internal break exists that is not visible from the outside (Correct answer)
The heating element requires AC voltage to measure resistance correctly
The ohmmeter battery is too weak to measure high-resistance elements

Correct answer: An internal break exists that is not visible from the outside

Resistance heating elements can develop internal breaks at connection points or within the sheathing that are invisible externally but create a complete open circuit detected by an ohmmeter.

Question 7: Under the Fair Labor Standards Act (FLSA), non-exempt employees must receive overtime pay at what rate for hours worked beyond 40 per week?

1.25 times the regular rate of pay
The same regular rate of pay
Double the regular rate of pay
1.5 times the regular rate of pay (Correct answer)

Correct answer: 1.5 times the regular rate of pay

The FLSA mandates that covered, non-exempt employees receive at least one and one-half times their regular hourly rate for all hours worked beyond 40 in a workweek.

Question 8: Which device is most effective for mitigating voltage sags caused by motor starting on a distribution system?

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

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

Article 700 (Correct answer)
Article 702
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 10: What is the minimum approach distance for an unqualified worker near energized 15 kV overhead conductors?

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

Correct answer: 10 feet

OSHA requires unqualified workers to maintain at least 10 feet from energized lines up to 50 kV.

Question 11: Which document establishes the minimum safety standards that a master electrician must follow for electrical installations in the United States?

ANSI/NECA 1
OSHA 29 CFR 1910
IEEE Std 1584
NFPA 70 (National Electrical Code) (Correct answer)

Correct answer: NFPA 70 (National Electrical Code)

NFPA 70, the National Electrical Code, is the foundational standard for safe electrical installation adopted by most US jurisdictions.

Question 12: 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 owner-builder or homeowner exemption (Correct answer)
The DIY exception under OSHA
The residential carve-out provision
The de minimis exemption

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 13: In an emergency where a worker's clothing catches fire from an arc flash, what is the correct immediate response?

The victim should stop, drop, and roll to smother the flames (Correct answer)
Bystanders should use a fire extinguisher directly on the victim's body
Douse the victim with any available liquid, including electrical coolant
The victim should run to the nearest exit to get fresh air

Correct answer: The victim should stop, drop, and roll to smother the flames

Stop, drop, and roll is the universally recommended technique to smother flames on a person's clothing and body.

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

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

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

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

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 16: What does the NEC require as the minimum number of 20A small appliance branch circuits for a residential kitchen per NEC 210.52(B)?

One 20A circuit
One circuit per 12 linear feet of counter
Two 20A circuits (Correct answer)
Three 20A circuits

Correct answer: Two 20A circuits

NEC 210.52(B)(1) requires a minimum of two 20A small appliance branch circuits for the kitchen receptacle outlets in a dwelling unit.

Question 17: A project owner requests a 'change order' that significantly increases the project scope. What should the master electrician do FIRST?

Begin the additional work immediately to maintain goodwill
Assess the cost and time impact, then negotiate and execute a written change order before proceeding (Correct answer)
Refuse the change and refer to the original contract scope
Contact the project's surety company for approval

Correct answer: Assess the cost and time impact, then negotiate and execute a written change order before proceeding

Before performing any scope changes, the electrician should evaluate impacts and get a written, signed change order to protect against unpaid work disputes.

Question 18: How does proper labeling of circuits aid in troubleshooting?

It helps identify and isolate circuits quickly, improving efficiency and safety. (Correct answer)
It speeds up the wiring process.
It makes the system look more organized.
It reduces the number of circuits in the system.

Correct answer: It helps identify and isolate circuits quickly, improving efficiency and safety.

Proper labeling of circuits is invaluable during troubleshooting because it allows technicians to quickly and accurately identify which circuit controls which specific load or area. This immediate identification enables efficient isolation of the problematic circuit without affecting others, speeding up the diagnostic process. Furthermore, it significantly enhances safety by ensuring that the correct circuit is de-energized before work begins, preventing accidental shocks.

Question 19: A disconnect switch blade shows significant discoloration and pitting at one phase only. After replacing the blade, what additional step is CRITICAL before returning to service?

Identify and correct the root cause of the overheating (Correct answer)
Verify the correct fuse size is installed in all three phases
Megohmmeter test all three phases of the downstream circuit
Apply anti-oxidant compound to all switch blades

Correct answer: Identify and correct the root cause of the overheating

Replacing only the damaged component without finding the root cause (loose connection, overloaded circuit, poor contact pressure) will result in recurrence of the same damage.

Question 20: Which NEC article governs the installation of energy storage systems (ESS) such as battery backup systems in commercial buildings?

NEC Article 706 (Correct answer)
NEC Article 700
NEC Article 480
NEC Article 625

Correct answer: NEC Article 706

NEC Article 706 specifically covers energy storage systems including battery-based systems, defining installation requirements for stationary storage.

Question 21: What action must a qualified electrician take before testing a capacitor bank that has been de-energized but not yet discharged?

Use an approved discharge resistor or discharge tool and verify zero voltage with a meter (Correct answer)
Wait at least 5 minutes for natural discharge before touching any terminals
Short the capacitor terminals with bare copper wire to discharge immediately
Test with a simple neon tester before using a digital multimeter

Correct answer: Use an approved discharge resistor or discharge tool and verify zero voltage with a meter

Capacitors retain lethal stored charge after de-energization; they must be discharged using an approved discharge resistor and then verified at zero voltage with a calibrated meter.

Question 22: Per NEC 700.12, an emergency system's alternate power source must be capable of supplying power within how many seconds of normal power failure?

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

Correct answer: 10 seconds

NEC 700.12 requires emergency systems to restore power within 10 seconds of normal supply failure.

Question 23: A 3-phase, 4-wire, 208Y/120V system supplies a balanced load of 60 A per phase at 208V line-to-line. What is the total three-phase kVA?

21.63 kVA (Correct answer)
25.96 kVA
37.44 kVA
14.98 kVA

Correct answer: 21.63 kVA

3-phase kVA = V_LL × I_L × √3 / 1000 = 208 × 60 × 1.732 / 1000 ≈ 21.63 kVA.

Question 24: A worker contacts an energized 480V conductor and is thrown clear. After calling 911, what is the rescuer's immediate priority?

Administer water to treat burns
Remove wet clothing to prevent further shock
Begin CPR only if the victim is unresponsive and not breathing (Correct answer)
Move the victim away from the electrical hazard using a non-conductive object if safe

Correct answer: Begin CPR only if the victim is unresponsive and not breathing

The rescuer should ensure the scene is safe, then begin CPR immediately if the victim is unresponsive and not breathing normally.

Question 25: 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)
Portable use only (Type SPT)
Hard usage (Type SO)
Indoor use only (Type SJO)

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 26: When installing an energy storage system (ESS) in a commercial building, which NEC article provides the specific installation requirements?

Article 480
Article 706 (Correct answer)
Article 710
Article 690

Correct answer: Article 706

NEC Article 706 covers stationary standby and energy storage systems including battery systems, flywheels, and capacitors used for energy storage.

Question 27: What is the purpose of a K-factor rating on a transformer serving nonlinear loads?

Defines the transformer's short-circuit withstand rating
Specifies the maximum inrush current tolerance
Indicates the transformer's ability to handle harmonic heating without derating (Correct answer)
Sets the insulation voltage class

Correct answer: Indicates the transformer's ability to handle harmonic heating without derating

A K-factor transformer is designed with additional thermal capacity to withstand the increased eddy current losses caused by harmonic currents.

Question 28: Per NEC 210.19(A)(1), branch circuit conductors serving continuous loads must be sized to what percentage of the continuous load current?

115%
125% (Correct answer)
100%
110%

Correct answer: 125%

NEC 210.19(A)(1) requires branch circuit conductors to have an ampacity not less than 125% of the continuous load to prevent thermal degradation.

Question 29: Which harmonic order is typically the most problematic in three-phase systems powered by six-pulse VFDs?

5th and 7th (Correct answer)
3rd and 9th
11th and 13th
2nd and 4th

Correct answer: 5th and 7th

Six-pulse rectifier drives characteristically generate dominant 5th and 7th order harmonics that can overheat transformers and trip protective relays.

Question 30: In a Class I, Division 1 hazardous location, which wiring method is specifically permitted per NEC 501.10(A)?

Threaded rigid metal conduit (RMC) or threaded steel intermediate metal conduit (IMC) (Correct answer)
Type MC cable with a PVC jacket
Electrical nonmetallic tubing (ENT)
Liquid-tight flexible nonmetallic conduit

Correct answer: Threaded rigid metal conduit (RMC) or threaded steel intermediate metal conduit (IMC)

NEC 501.10(A)(1) requires threaded rigid metal conduit or threaded steel IMC as the primary wiring method for Class I, Division 1 locations.

Question 31: NEC 680.26 requires equipotential bonding for all metal parts within what distance of the inside walls of a swimming pool?

10 feet
3 feet
5 feet (Correct answer)
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 32: 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?

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

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 33: When two qualified electricians perform group lockout/tagout, what must each individual do?

Rely on one lockout and one tagout
Apply their own personal lock to a hasp on each energy isolation point (Correct answer)
Use color-coded tags in lieu of individual locks
Share a single lock assigned to the supervisor

Correct answer: Apply their own personal lock to a hasp on each energy isolation point

Group LOTO requires each individual to apply their own personal lock to the hasp so no single person can inadvertently restore energy.

Question 34: 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 AWG
2/0 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 35: Per NEC 240.4(D), what is the maximum overcurrent protection permitted for a 12 AWG copper branch-circuit conductor?

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

Correct answer: 20A

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

Question 36: Which federal law requires employers to record and report work-related injuries and illnesses, affecting electrical contractors' safety documentation?

The Fair Labor Standards Act (FLSA)
The Occupational Safety and Health Act (OSH Act) (Correct answer)
The National Electrical Safety Code (NESC)
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 37: A 4,000 sq ft retail store (NEC occupancy: stores) has 80 general-use duplex receptacles. Using NEC 220.14(H), what is the receptacle load?

14,400 VA (Correct answer)
21,600 VA
28,800 VA
7,200 VA

Correct answer: 14,400 VA

NEC 220.14(H) counts each single or duplex receptacle outlet as 180 VA; 80 outlets × 180 VA = 14,400 VA.

Question 38: A contractor performs electrical work without pulling a required permit. Under most state licensing laws, this is grounds for:

A verbal warning only
Suspension or revocation of the electrical license (Correct answer)
Mandatory re-examination
Automatic criminal prosecution only

Correct answer: Suspension or revocation of the electrical license

Performing work without required permits typically constitutes a violation of state licensing law, which can result in suspension or revocation of the license.

Question 39: A master electrician uses the 'percentage of completion' method for revenue recognition. When is revenue recorded?

When the final invoice is submitted
Only when the project is fully complete and accepted
Proportionally as project work progresses based on costs incurred or milestones reached (Correct answer)
When the client signs the contract

Correct answer: Proportionally as project work progresses based on costs incurred or milestones reached

The percentage-of-completion method recognizes revenue incrementally as work is performed, matching income to project progress rather than waiting for full completion.

Question 40: When a journeyman under a master electrician's supervision reports an unsafe condition on the job site, the master electrician should:

Notify the owner but continue work
Ask the journeyman to document it after the shift
Dismiss the concern to avoid delays
Investigate the report and take corrective action before resuming that portion of the work (Correct answer)

Correct answer: Investigate the report and take corrective action before resuming that portion of the work

Prompt investigation and correction of reported unsafe conditions is both an ethical duty and an OSHA requirement.

Question 41: 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 42: Per NEC 110.9, equipment used to interrupt fault current must have an interrupting rating that is:

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

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 43: What is the purpose of a system bonding jumper in a separately derived system per NEC 250.30?

To connect parallel conductors together
To provide a low-impedance fault current path to utility ground
To bond the neutral conductor to the transformer case
To connect the grounded conductor to the equipment grounding conductor at the source (Correct answer)

Correct answer: To connect the grounded conductor to the equipment grounding conductor at the source

The system bonding jumper connects the grounded conductor (neutral) to the equipment grounding conductor and to the enclosure at the source of a separately derived system.

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?

6 AWG or smaller (Correct answer)
4 AWG or smaller
10 AWG or smaller
8 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: When conductors are installed in parallel in multiple raceways, how must equipment grounding conductors be installed per NEC 250.122(F)?

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)
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 46: Per NEC 220.61, the neutral load for a feeder or service shall be the maximum unbalance of the load. For 3-wire, 2-phase circuits, the neutral carries current only when:

The power factor is leading
Phases are balanced
The system is delta-connected
Phases are unbalanced (Correct answer)

Correct answer: Phases are unbalanced

The neutral conductor in a multi-wire branch circuit or feeder carries only the unbalanced portion of the load between phases.

Question 47: 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 plane must be connected to the electrical grounding system with a copper conductor, not smaller than 8 AWG. (Correct answer)
The equipotential plane is only required if the building has a metal frame.

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 48: According to NEC 210.8(A), GFCI protection is required for all 125-volt, single-phase, 15- and 20-ampere receptacles in dwelling unit bathrooms. This requirement applies to which locations additionally?

Living rooms and bedrooms
Only where within 6 feet of a water source
Hallways and stairwells only
Garages, outdoors, crawl spaces, unfinished basements, kitchens, boathouses, and laundry areas (Correct answer)

Correct answer: Garages, outdoors, crawl spaces, unfinished basements, kitchens, boathouses, and laundry areas

NEC 210.8(A) lists bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, boathouses, and laundry areas as locations requiring GFCI protection in dwelling units.

Question 49: A power quality meter shows significant 3rd harmonic current (180 Hz) on a 60 Hz system. What type of load is MOST likely causing this?

Single-phase switch-mode power supplies (computers, electronics) (Correct answer)
Resistive heating elements such as electric baseboard heaters
Three-phase induction motors running at full load
Synchronous capacitors for power factor correction

Correct answer: Single-phase switch-mode power supplies (computers, electronics)

Single-phase switch-mode power supplies draw current in pulses rather than sinusoidally, generating high levels of 3rd harmonic and other odd-order harmonics on the system.

Question 50: Per NEC 250.70, connections of grounding electrode conductors to grounding electrodes must be made using:

Wire nuts rated for outdoor use
Mechanical set-screw connectors only
Any UL-listed wire connector rated for the conductor size
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 51: An electrician discovers a coworker unresponsive after contact with a live panel. The scene is confirmed safe. What is the correct sequence of actions?

Use AED first, then call 911, then begin CPR
Call 911, check responsiveness, begin CPR if needed, use AED if available (Correct answer)
Wait for EMS before touching the victim to avoid liability
Begin CPR immediately, then call 911 after two minutes

Correct answer: Call 911, check responsiveness, begin CPR if needed, use AED if available

The correct chain of survival is: call 911, assess the victim, begin CPR if needed, and deploy an AED as soon as possible.

Question 52: In a fire pump installation, what is the minimum voltage drop permitted at the motor terminals under locked-rotor conditions?

Voltage must not drop below 65% of motor nameplate voltage (Correct answer)
5% voltage drop
Voltage must not drop below 70% of motor nameplate voltage
15% voltage drop

Correct answer: Voltage must not drop below 65% of motor nameplate voltage

NFPA 20 and NEC 695.7 require that the voltage at fire pump motor terminals shall not drop below 65% of nameplate voltage under locked-rotor conditions.

Question 53: A facility's power factor is measured at 0.72 lagging. What is the most efficient corrective action for a master electrician to recommend?

Install capacitor banks at the load (Correct answer)
Install additional transformers
Add resistive heating loads
Replace conductors with larger gauge

Correct answer: Install capacitor banks at the load

Capacitor banks supply leading reactive current that cancels the lagging reactive demand, improving power factor toward unity.

Question 54: 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)
Plate electrode
Concrete-encased electrode
Ground rod driven 8 feet into earth

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 55: Which of the following is explicitly prohibited as a grounding electrode per NEC 250.52(B)?

Ground ring
Concrete-encased electrode
Metal water pipe with 10+ feet in soil
Metal underground gas piping system (Correct answer)

Correct answer: Metal underground gas piping system

NEC 250.52(B) explicitly prohibits metal underground gas piping systems from being used as grounding electrodes due to safety hazards.

Question 56: Which practice BEST demonstrates due diligence by a master electrician before starting a renovation project in a building constructed prior to 1980?

Begin work and note any hazards as encountered
Limit work to new wiring to avoid disturbing old materials
Arrange for testing and proper disclosure of potential asbestos and lead paint hazards before disturbing materials (Correct answer)
Assume modern materials were used in previous renovations

Correct answer: Arrange for testing and proper disclosure of potential asbestos and lead paint hazards before disturbing materials

Pre-1980 buildings may contain asbestos and lead paint; identifying these hazards before disturbing materials protects workers and building occupants.

Question 57: In a Class II, Division 1 location involving combustible dust, what type of enclosure is required for electrical equipment?

Explosionproof
Weatherproof
Dust-ignitionproof (Correct answer)
Rainproof

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 58: A permit-required confined space containing electrical equipment must be monitored for which atmospheric hazard before and during entry?

Hydrogen sulfide only, as it is the most common confined space hazard
Oxygen deficiency/enrichment, flammable gases, and toxic contaminants (Correct answer)
Oxygen level only, as electrical equipment does not produce toxic gases
Carbon dioxide concentration only

Correct answer: Oxygen deficiency/enrichment, flammable gases, and toxic contaminants

OSHA 29 CFR 1910.146 requires continuous monitoring of oxygen levels, flammable gas concentrations, and toxic atmospheric contaminants in permit-required confined spaces.

Question 59: When designing a service entrance for a commercial building, what is the minimum clearance required above a flat roof (not readily accessible) for service-drop conductors per NEC 230.24?

10 feet
18 inches
8 feet
3 feet (Correct answer)

Correct answer: 3 feet

NEC 230.24(A) Exception No. 2 permits 3 feet above a roof not readily accessible where the voltage does not exceed 300V between conductors.

Question 60: What is the primary purpose of a code of ethics in CME practice?

To establish professional standards of conduct and guide decision-making in ethical dilemmas (Correct answer)
To set pricing for services
To define office hours
To determine salary structures

Correct answer: To establish professional standards of conduct and guide decision-making in ethical dilemmas

A code of ethics provides a framework of professional values and behavioral standards that guides practitioners in making ethical decisions, maintaining public trust, and upholding the integrity of the profession.

Question 61: A supply-side bonding jumper is used to bond metal enclosures on which side of the service or separately derived system?

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

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 62: What NEC article covers the installation of transformers and transformer vaults?

Article 490
Article 460
Article 450 (Correct answer)
Article 480

Correct answer: Article 450

NEC Article 450 covers transformers and transformer vaults, including their installation requirements.

Question 63: What is the maximum length of a flexible connection permitted between rigid conduit and a motor to allow for vibration isolation per NEC 430.245(B)?

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

Correct answer: 36 inches

NEC 430.245(B) permits flexible conduit connections up to 36 inches in length at motor terminals to allow for vibration, misalignment, or interchangeability.

Question 64: NEC 334.10 permits Type NM cable (Romex) in which of the following structures?

One- and two-family dwellings and multifamily dwellings up to and including three floors above grade (Correct answer)
Commercial buildings under 10,000 square feet
Any structure with a sprinkler system
Buildings exceeding three floors above grade

Correct answer: One- and two-family dwellings and multifamily dwellings up to and including three floors above grade

NEC 334.10(A) permits NM cable in one- and two-family dwellings and multifamily dwellings that are not more than three floors above grade.

Question 65: For a system to be considered selectively coordinated, which of the following must occur during a fault condition?

All overcurrent protective devices in the fault path must open simultaneously.
The main service disconnect and the branch circuit breaker must both trip.
The overcurrent protective device immediately upstream of the fault must open, while all further upstream devices remain closed. (Correct answer)
The overcurrent protective device nearest to the source must open first.

Correct answer: The overcurrent protective device immediately upstream of the fault must open, while all further upstream devices remain closed.

Selective coordination is the localization of an overcurrent condition to restrict outages to the circuit or equipment affected. This is achieved by selecting and setting overcurrent protective devices so that the device closest to the fault on the line side (immediately upstream) opens first, leaving the rest of the system operational. NEC 700.32 mandates this for emergency systems.

Question 66: In a commercial kitchen, what classification applies to the area within 18 inches of a cooking surface exhaust hood opening per NFPA 96 and NEC 500?

Class I, Division 2
Unclassified if proper ventilation is maintained (Correct answer)
Class I, Division 1
Class II, Division 1

Correct answer: Unclassified if proper ventilation is maintained

Properly ventilated commercial kitchen cooking areas are typically unclassified when NFPA 96 ventilation requirements are met, as the exhaust system removes flammable vapors.

Question 67: What is the acceptable range of Total Harmonic Distortion (THD) for voltage at a point of common coupling per IEEE 519?

Less than 10%
Less than 15%
Less than 5% (Correct answer)
Less than 20%

Correct answer: Less than 5%

IEEE 519 specifies that voltage THD at the point of common coupling should be less than 5% for systems below 69 kV.

Question 68: 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
6 feet
3 feet
3.5 feet (Correct answer)

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 69: What is the role of documentation in troubleshooting electrical systems?

It is only needed for compliance purposes.
It reduces the need for inspections.
It provides valuable information for future troubleshooting and system improvements. (Correct answer)
It is only necessary for system installations.

Correct answer: It provides valuable information for future troubleshooting and system improvements.

Documentation plays a critical role in troubleshooting electrical systems by providing a comprehensive historical record of the installation, previous repairs, modifications, and test results. This information, including schematics, wiring diagrams, and maintenance logs, offers valuable insights for diagnosing current issues and understanding system behavior. Good documentation streamlines future troubleshooting efforts, reduces downtime, and supports informed decisions for system improvements and upgrades.

Question 70: 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
1000A (Correct answer)
100A
800A

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 71: Under ASHRAE 90.1, which lighting control strategy is REQUIRED for commercial spaces greater than 5,000 sq ft?

Dimmable ballasts only
Occupancy sensors only
Daylight harvesting only
Automatic shutoff controls (Correct answer)

Correct answer: Automatic shutoff controls

ASHRAE 90.1 mandates automatic shutoff controls (occupancy sensors or time scheduling) for commercial spaces exceeding 5,000 sq ft to reduce energy waste.

Question 72: An electrician is installing 125-volt, single-phase, 20-ampere receptacles to provide shore power to boat slips at a new marina. What specific requirement must these receptacles meet per NEC Article 555?

Each receptacle must be located at least 48 inches above the dock surface.
Each receptacle must be of the locking and weather-resistant type.
Each receptacle must be supplied by a multi-wire branch circuit.
Each single receptacle providing shore power must be provided with GFCI protection. (Correct answer)

Correct answer: Each single receptacle providing shore power must be provided with GFCI protection.

NEC 555.33(A) requires that 125-volt and 125/250-volt, single-phase, 15-, 20-, 30-, and 50-ampere receptacles that provide shore power for boats be protected by a ground-fault circuit-interrupter. This is a critical safety measure in a wet environment to protect against electric shock drowning (ESD).

Question 73: Per NEC 680.22, what type of receptacles are required within 6 to 10 feet of the inside walls of a permanently installed swimming pool?

No receptacles are permitted in this zone
Standard duplex receptacles
GFCI-protected receptacles (Correct answer)
Twist-lock receptacles only

Correct answer: GFCI-protected receptacles

NEC 680.22(A)(1) requires all receptacles located between 6 and 10 feet of a permanently installed pool to be GFCI protected.

Question 74: A master electrician notices a worker using a ground prong adapter ('cheater plug') on a power tool. What is the primary danger?

Reducing tool motor efficiency
Overloading the circuit
Eliminating the equipment grounding path, removing fault current protection (Correct answer)
Causing a voltage drop on the circuit

Correct answer: Eliminating the equipment grounding path, removing fault current protection

A cheater plug removes the equipment grounding conductor, eliminating the fault current path and leaving the tool casing potentially energized.

Question 75: Why is proper labeling of electrical systems important for safety?

To increase the system's energy efficiency.
To focus on aesthetic improvements.
To reduce system complexity.
To ensure easy identification of circuits and systems for safety. (Correct answer)

Correct answer: To ensure easy identification of circuits and systems for safety.

Proper labeling of electrical systems is crucial for safety as it allows for quick and accurate identification of circuits, components, and their functions. Clearly marked panels, wires, and devices enable electricians to safely de-energize specific circuits before working on them, preventing accidental shocks or damage. This clarity is vital during maintenance, troubleshooting, and emergency situations, enhancing overall safety and efficiency.

Question 76: What is the purpose of grounding in electrical systems?

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

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

Grounding provides a safe path for fault currents to flow directly to the earth, bypassing sensitive equipment and preventing dangerous voltage buildup on conductive surfaces. In the event of an electrical fault, grounding quickly trips protective devices like circuit breakers, minimizing the risk of electrical shock to individuals and preventing damage to electrical components. It is a cornerstone of electrical safety.

Question 77: Per NEC 250.30, where must the system bonding jumper be installed for a separately derived system?

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

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 78: 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 79: OSHA 1926.416 requires that before electrical work begins, the qualified person must determine the nominal voltage of exposed live parts. What minimum insulated tool rating is required for work on systems up to 1,000V?

2,000V rated
500V rated
1,500V rated
1,000V rated (Correct answer)

Correct answer: 1,000V rated

Insulated tools used on systems up to 1,000V must be rated for at least 1,000V per OSHA construction electrical safety requirements.

Question 80: When designing a branch circuit for a household cooking range rated at 12 kW, what is the calculated demand load per NEC Table 220.55?

12 kW
8.4 kW
8 kW (Correct answer)
10 kW

Correct answer: 8 kW

NEC Table 220.55 Column C specifies 8 kW demand load for a single household cooking range rated 12 kW.

Question 81: NEC Article 708 Critical Operations Power Systems (COPS) apply to facilities that:

Exceed 50,000 square feet of floor area
Have more than 1,000 occupants
Contain medical imaging equipment
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 82: What is the purpose of performing a dielectric absorption ratio (DAR) test during insulation resistance testing?

To determine the conductor resistance of the cable under test
To calibrate the megohmmeter before the main insulation test
To measure the exact capacitance of cable insulation
To identify moisture or contamination in insulation by comparing 30-second and 60-second readings (Correct answer)

Correct answer: To identify moisture or contamination in insulation by comparing 30-second and 60-second readings

The DAR compares the 30-second to 60-second megohmmeter readings; a ratio near 1.0 indicates moisture or contaminated insulation, while clean dry insulation shows significantly higher readings at 60 seconds.

Question 83: Under NEC 445.13, the minimum conductor ampacity for generator output terminals must be at least what percentage of the generator's nameplate current rating?

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

Correct answer: 115%

NEC 445.13 requires that conductors from generator terminals have an ampacity of not less than 115% of the nameplate current rating of the generator.

Question 84: Under the NEC, a 'qualified person' performing electrical work must demonstrate knowledge and skills related to:

Only the specific equipment being serviced
Construction and operation of equipment and the hazards involved (Correct answer)
Completion of a four-year apprenticeship program
Certification by a state licensing board

Correct answer: Construction and operation of equipment and the hazards involved

NEC Article 100 defines a qualified person as one with skills and knowledge of the construction and operation of equipment and the hazards involved.

Question 85: A GFCI receptacle will not reset and the test button does not trip it. What is the MOST likely cause?

There is a ground fault downstream on the load side
The circuit breaker protecting the circuit is undersized
The GFCI device has failed and must be replaced (Correct answer)
The GFCI is wired with line and load terminals reversed

Correct answer: The GFCI device has failed and must be replaced

A GFCI that will not reset and whose test button produces no response has an internal failure and must be replaced — the device's self-test circuitry is non-functional.

Question 86: Which NEC article covers the special requirements for electrical installations in Class I, Division 1 hazardous locations?

Article 501 (Correct answer)
Article 500
Article 502
Article 503

Correct answer: Article 501

NEC Article 501 specifically covers Class I (flammable gas/vapor) hazardous locations in Divisions 1 and 2.

Question 87: When responding to an electrical fire in an energized panel, the first action should be to:

Call 911 and wait for the fire department before taking any action
Apply a CO₂ extinguisher immediately to cool the panel
De-energize the circuit at the upstream disconnect or main breaker if safely possible (Correct answer)
Open the panel door to improve ventilation and cool the components

Correct answer: De-energize the circuit at the upstream disconnect or main breaker if safely possible

The safest first response is to de-energize the panel at the upstream source, converting it to a non-electrical fire before applying extinguishing agents.

Question 88: In a commercial garage used for repair and service where adequate ventilation is not provided, what is the default classification for the area extending from the floor up to a level of 18 inches?

Class I, Division 2. (Correct answer)
Class II, Division 1.
Class I, Division 1.
Unclassified.

Correct answer: Class I, Division 2.

Per NEC 511.3(C)(1)(b), in a major repair garage without four or more air changes per hour, the area from the floor up to 18 inches is classified as a Class I, Division 2 location. This is because flammable gasoline vapors are heavier than air and can accumulate near the floor. Any pit or depression below floor level is considered Class I, Division 1.

Question 89: Under most state contractor licensing laws, which of the following is typically required before a contractor can legally bid on commercial electrical work?

Only a business license
A licensed Master or Journeyman Electrician on staff and proper contractor license (Correct answer)
OSHA 30-hour certification for all employees
Registration with NFPA

Correct answer: A licensed Master or Journeyman Electrician on staff and proper contractor license

Most states require electrical contractors to hold a contractor license and employ or be a licensed Master Electrician to legally perform and bid commercial electrical work.

Question 90: Which NEC article addresses the general requirements for examination, identification, installation, and use of electrical equipment?

Article 90
Article 110 (Correct answer)
Article 100
Article 200

Correct answer: Article 110

NEC Article 110 covers general requirements including equipment approval, examination, identification, installation, and working space requirements.

Question 91: Per NEC 220.87, what is the permitted method for determining the existing load on a service for the purpose of adding new loads?

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 80% of the service rating
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 92: Per NEC 250.119, equipment grounding conductors must be identified by which of the following?

White or gray insulation only
Green insulation, green with yellow stripes, or bare conductor (Correct answer)
Orange insulation for systems above 250V
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 93: A 3,600 sq ft dwelling has a 12 kW range. Using the NEC Table 220.55 demand factor, what is the demand load for the range?

12,000 W
10,800 W
8,000 W
8,400 W (Correct answer)

Correct answer: 8,400 W

NEC Table 220.55 for a single range rated 12 kW (over 8.75 kW) uses Column C: 8 kW + 5% per kW over 12 kW, but for exactly 12 kW the demand is 8,400 W per the note (8 kW + 400 W).

Question 94: NEC 800.100 requires primary protectors for communications circuits entering buildings. Where must the primary protector be located?

At the telephone company's nearest pole
In the telephone room on the top floor
At the main electrical panel
As close as practicable to the point at which the cable enters the building (Correct answer)

Correct answer: As close as practicable to the point at which the cable enters the building

NEC 800.100(A) requires primary protectors to be located as close as practicable to the point where the communications cable enters the building to limit exposure.

Question 95: 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)?

20 feet (Correct answer)
25 feet
15 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 96: Which of the following wiring methods is permitted to be installed exposed in a space used for environmental air handling above a lay-in ceiling (plenum), without being installed in a raceway?

Type AC (Armored Cable) (Correct answer)
Service-entrance cable (Type SE)
Non-metallic sheathed cable (Type NM-B)
Type MC cable with an overall nonmetallic covering

Correct answer: Type AC (Armored Cable)

According to NEC 300.22(C), wiring in 'Other Spaces Used for Environmental Air (Plenums)' is restricted to specific methods to limit the spread of fire and smoke. Permitted methods without a raceway include Type AC cable, Type MC cable without an overall nonmetallic covering, and other specifically listed plenum-rated cables. Type NM-B and Type SE are not permitted in plenums.

Question 97: Under OSHA 1910.137, insulated rubber gloves must be electrically tested at intervals not exceeding how many months?

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

Correct answer: 6 months

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

Question 98: What is the primary function of the equipment grounding conductor (EGC) in a branch circuit?

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

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

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

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: NEC 358 covers which type of raceway?

Rigid PVC conduit
Flexible metallic conduit
Electrical metallic tubing (EMT) (Correct answer)
Liquidtight flexible nonmetallic conduit

Correct answer: Electrical metallic tubing (EMT)

NEC Article 358 covers Electrical Metallic Tubing (EMT), including its use, installation, and fittings.

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%

To Pass

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