Electrical Wiring Commercial 18th Edition
exam Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
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1. What is the primary purpose of an equipment grounding
conductor in a commercial electrical installation?
A. To carry normal load current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce conductor resistance
Answer: C. To provide a low-impedance path for fault current
Rationale: An equipment grounding conductor provides a conductive
path for fault current back to the source so that overcurrent protective
devices can operate promptly. It is not intended to carry normal
operating current.
, 2. Which type of wiring method is commonly used where conductors
require mechanical protection in commercial installations?
A. Open-air cord
B. Raceway
C. Bare conductor
D. Temporary lamp cord
Answer: B. Raceway
Rationale: Raceways protect conductors from physical damage and
provide an organized pathway for wiring. Common commercial
raceways include electrical metallic tubing, rigid metal conduit,
intermediate metal conduit, and various nonmetallic systems.
3. What is the main function of an overcurrent protective device?
A. Increase available voltage
B. Prevent excessive current from damaging conductors and equipment
C. Improve power factor
D. Provide mechanical support for conductors
Answer: B. Prevent excessive current from damaging conductors and
equipment
,Rationale: Fuses and circuit breakers protect electrical conductors and
equipment against excessive current caused by overloads or short
circuits. Proper sizing helps prevent overheating and fire hazards.
4. In a three-phase commercial system, what is the phase
relationship between the three phase voltages?
A. 60 degrees
B. 90 degrees
C. 120 degrees
D. 180 degrees
Answer: C. 120 degrees
Rationale: The three sinusoidal voltages in a balanced three-phase
system are separated by 120 electrical degrees. This arrangement
provides efficient power transmission and smooth power delivery to
three-phase loads.
5. What is the purpose of a junction box?
A. To increase circuit voltage
B. To provide a protected enclosure for conductor connections
C. To replace overcurrent protection
D. To eliminate grounding requirements
, Answer: B. To provide a protected enclosure for conductor
connections
Rationale: Junction boxes enclose splices and conductor terminations,
protecting connections from physical damage and accidental contact.
They also provide an accessible location for making and maintaining
connections.
6. Which conductor is normally identified as the grounded
conductor in an AC branch circuit?
A. Green
B. Bare copper
C. White or gray
D. Orange only
Answer: C. White or gray
Rationale: The grounded circuit conductor is generally identified by
white or gray insulation or other permitted identification methods.
Green or bare conductors are generally associated with equipment
grounding.
7. What is the primary purpose of a disconnecting means?
A. To increase circuit capacity
B. To isolate equipment from its source of power
exam Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of an equipment grounding
conductor in a commercial electrical installation?
A. To carry normal load current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce conductor resistance
Answer: C. To provide a low-impedance path for fault current
Rationale: An equipment grounding conductor provides a conductive
path for fault current back to the source so that overcurrent protective
devices can operate promptly. It is not intended to carry normal
operating current.
, 2. Which type of wiring method is commonly used where conductors
require mechanical protection in commercial installations?
A. Open-air cord
B. Raceway
C. Bare conductor
D. Temporary lamp cord
Answer: B. Raceway
Rationale: Raceways protect conductors from physical damage and
provide an organized pathway for wiring. Common commercial
raceways include electrical metallic tubing, rigid metal conduit,
intermediate metal conduit, and various nonmetallic systems.
3. What is the main function of an overcurrent protective device?
A. Increase available voltage
B. Prevent excessive current from damaging conductors and equipment
C. Improve power factor
D. Provide mechanical support for conductors
Answer: B. Prevent excessive current from damaging conductors and
equipment
,Rationale: Fuses and circuit breakers protect electrical conductors and
equipment against excessive current caused by overloads or short
circuits. Proper sizing helps prevent overheating and fire hazards.
4. In a three-phase commercial system, what is the phase
relationship between the three phase voltages?
A. 60 degrees
B. 90 degrees
C. 120 degrees
D. 180 degrees
Answer: C. 120 degrees
Rationale: The three sinusoidal voltages in a balanced three-phase
system are separated by 120 electrical degrees. This arrangement
provides efficient power transmission and smooth power delivery to
three-phase loads.
5. What is the purpose of a junction box?
A. To increase circuit voltage
B. To provide a protected enclosure for conductor connections
C. To replace overcurrent protection
D. To eliminate grounding requirements
, Answer: B. To provide a protected enclosure for conductor
connections
Rationale: Junction boxes enclose splices and conductor terminations,
protecting connections from physical damage and accidental contact.
They also provide an accessible location for making and maintaining
connections.
6. Which conductor is normally identified as the grounded
conductor in an AC branch circuit?
A. Green
B. Bare copper
C. White or gray
D. Orange only
Answer: C. White or gray
Rationale: The grounded circuit conductor is generally identified by
white or gray insulation or other permitted identification methods.
Green or bare conductors are generally associated with equipment
grounding.
7. What is the primary purpose of a disconnecting means?
A. To increase circuit capacity
B. To isolate equipment from its source of power
