AZ L-77 Industrial Electrical Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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1. What is the primary purpose of a circuit breaker in an industrial
electrical system?
a. Increase circuit voltage
b. Improve power factor
c. Provide overcurrent protection
d. Reduce conductor resistance
Answer: c. Provide overcurrent protection
Rationale: A circuit breaker is designed to interrupt current when an
overload or short circuit occurs. By opening the circuit during an
abnormal current condition, it protects conductors, equipment, and
personnel from damage and fire hazards.
,2. Which instrument is commonly used to measure electrical current
without disconnecting the conductor?
a. Megohmmeter
b. Clamp meter
c. Oscilloscope
d. Watt-hour meter
Answer: b. Clamp meter
Rationale: A clamp meter measures current by sensing the magnetic
field surrounding a conductor. This allows measurements to be made
without opening or interrupting the circuit, making it particularly
useful for industrial troubleshooting.
3. What is the function of an equipment grounding conductor?
a. Carry normal load current
b. Increase circuit voltage
c. Provide a low-impedance path for fault current
d. Control motor speed
Answer: c. Provide a low-impedance path for fault current
Rationale: The equipment grounding conductor provides a conductive
path for fault current back to the source. This facilitates operation of
,overcurrent protective devices and helps keep exposed metal parts at
a safer electrical potential.
4. A three-phase motor rotates in the wrong direction. What is the
usual corrective action?
a. Increase the fuse size
b. Reverse any two phase conductors
c. Disconnect the grounding conductor
d. Replace the overload relay
Answer: b. Reverse any two phase conductors
Rationale: The direction of rotation of a three-phase motor depends
on phase sequence. Interchanging any two phase conductors reverses
the phase sequence and therefore reverses motor rotation.
5. What device is commonly used to control a large motor from a low-
current control circuit?
a. Contactor
b. Transformer fuse
c. Receptacle
d. Disconnect enclosure
Answer: a. Contactor
, Rationale: A contactor uses an electrically operated coil to open and
close power contacts. Its control circuit can use relatively low current
while the contacts switch the substantially higher current required by
an industrial motor.
6. What is the primary function of a motor overload relay?
a. Protect against every short circuit
b. Protect the motor from sustained overload conditions
c. Increase starting voltage
d. Provide equipment grounding
Answer: b. Protect the motor from sustained overload conditions
Rationale: Overload relays are designed to respond to excessive motor
current over time, which can cause overheating. Short-circuit
protection is normally provided separately by fuses or circuit breakers.
7. Which type of transformer is used to reduce voltage from a higher
level to a lower level?
a. Step-down transformer
b. Current transformer
c. Isolation transformer only
d. Step-up transformer
Answer: a. Step-down transformer
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. What is the primary purpose of a circuit breaker in an industrial
electrical system?
a. Increase circuit voltage
b. Improve power factor
c. Provide overcurrent protection
d. Reduce conductor resistance
Answer: c. Provide overcurrent protection
Rationale: A circuit breaker is designed to interrupt current when an
overload or short circuit occurs. By opening the circuit during an
abnormal current condition, it protects conductors, equipment, and
personnel from damage and fire hazards.
,2. Which instrument is commonly used to measure electrical current
without disconnecting the conductor?
a. Megohmmeter
b. Clamp meter
c. Oscilloscope
d. Watt-hour meter
Answer: b. Clamp meter
Rationale: A clamp meter measures current by sensing the magnetic
field surrounding a conductor. This allows measurements to be made
without opening or interrupting the circuit, making it particularly
useful for industrial troubleshooting.
3. What is the function of an equipment grounding conductor?
a. Carry normal load current
b. Increase circuit voltage
c. Provide a low-impedance path for fault current
d. Control motor speed
Answer: c. Provide a low-impedance path for fault current
Rationale: The equipment grounding conductor provides a conductive
path for fault current back to the source. This facilitates operation of
,overcurrent protective devices and helps keep exposed metal parts at
a safer electrical potential.
4. A three-phase motor rotates in the wrong direction. What is the
usual corrective action?
a. Increase the fuse size
b. Reverse any two phase conductors
c. Disconnect the grounding conductor
d. Replace the overload relay
Answer: b. Reverse any two phase conductors
Rationale: The direction of rotation of a three-phase motor depends
on phase sequence. Interchanging any two phase conductors reverses
the phase sequence and therefore reverses motor rotation.
5. What device is commonly used to control a large motor from a low-
current control circuit?
a. Contactor
b. Transformer fuse
c. Receptacle
d. Disconnect enclosure
Answer: a. Contactor
, Rationale: A contactor uses an electrically operated coil to open and
close power contacts. Its control circuit can use relatively low current
while the contacts switch the substantially higher current required by
an industrial motor.
6. What is the primary function of a motor overload relay?
a. Protect against every short circuit
b. Protect the motor from sustained overload conditions
c. Increase starting voltage
d. Provide equipment grounding
Answer: b. Protect the motor from sustained overload conditions
Rationale: Overload relays are designed to respond to excessive motor
current over time, which can cause overheating. Short-circuit
protection is normally provided separately by fuses or circuit breakers.
7. Which type of transformer is used to reduce voltage from a higher
level to a lower level?
a. Step-down transformer
b. Current transformer
c. Isolation transformer only
d. Step-up transformer
Answer: a. Step-down transformer
