LADWP CONSTRUCTION ELECTRICAL
MECHANIC EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A construction electrical mechanic is preparing to replace a damaged
480-volt, three-phase motor starter. The disconnect supplying the starter
is opened, locked, and tagged. Before touching any conductors, which
procedure provides the most appropriate verification that the circuit is
actually de-energized?
A. Check that the starter's pilot light is extinguished.
B. Use a properly rated voltage tester to test the circuit for absence of
voltage, including phase-to-phase and phase-to-ground as appropriate,
after verifying the tester on a known energized source.
C. Measure resistance between the three phases with an ohmmeter.
D. Press the motor start button and verify that the motor does not rotate.
Answer: B.
Rationale: The absence of a pilot light or motor operation does not
prove that hazardous voltage is absent. A properly rated test
instrument must be used to verify de-energization, and the tester itself
should be verified before and after the test when required by the
applicable electrical-safety procedure. Resistance testing is not an
acceptable substitute for voltage verification on an energized or
potentially energized circuit.
,2.
A 120/208-volt, three-phase, four-wire system supplies several
construction receptacles. A mechanic discovers that one branch circuit
has approximately 208 volts between two ungrounded conductors but
approximately 120 volts from either ungrounded conductor to the
neutral. What does this measurement indicate?
A. The transformer secondary is incorrectly connected.
B. The system is necessarily a 240/120-volt single-phase system.
C. The system is consistent with a 120/208-volt three-phase wye
configuration.
D. The neutral conductor is shorted to the equipment grounding
conductor.
Answer: C.
Rationale: In a typical 120/208-volt wye system, each phase measures
approximately 120 volts to the neutral, while two phase conductors
measure approximately 208 volts from one another. This relationship
results from the 120-degree phase displacement of the three-phase
system.
3.
A mechanic is installing metallic conduit for a 480-volt motor circuit.
The conduit is properly connected at both ends, but a section contains a
poorly installed coupling with significant mechanical damage. Why
should this condition be corrected even if the circuit conductors are
properly insulated?
A. Conduit is used only to provide mechanical protection, so the
coupling has no electrical significance.
B. A damaged coupling can compromise the mechanical integrity and
,continuity of the raceway and may interfere with the effective
grounding/bonding path.
C. The coupling will automatically increase motor current.
D. The damaged coupling will change the motor's phase sequence.
Answer: B.
Rationale: Metallic raceways can form part of the equipment
grounding and bonding path. Damaged or improperly assembled
fittings can compromise both physical protection and electrical
continuity. The condition should be repaired before the installation is
placed into service.
4.
A three-phase motor rotates opposite the desired direction after
installation. The supply voltage and frequency are correct, and the motor
has been inspected for mechanical problems. What is the standard
electrical correction for reversing the rotation of a typical three-phase
induction motor?
A. Reverse the neutral conductor.
B. Swap any two of the three phase conductors supplying the motor.
C. Increase the motor's overload setting.
D. Disconnect the equipment grounding conductor.
Answer: B.
Rationale: Reversing any two phase conductors changes the phase
sequence presented to a three-phase motor and reverses its rotational
direction. The equipment grounding conductor and protective devices
should never be altered as a means of correcting rotation.
5.
, A motor draws substantially higher current than expected immediately
after startup and quickly trips its overload protection. The shaft turns
freely by hand when the motor is disconnected. Which condition should
be investigated first?
A. Incorrect phase sequence only
B. Possible single-phasing, incorrect voltage, winding problems, or an
electrical connection fault
C. Excessive conduit diameter
D. Incorrect color of the grounding conductor
Answer: B.
Rationale: Excessive motor current can result from abnormal supply
voltage, loss of a phase, winding faults, incorrect connections, or
excessive mechanical load. Since the shaft turns freely, electrical
causes deserve immediate attention. Single-phasing is particularly
dangerous because it can produce severe overheating.
6.
A mechanic is troubleshooting a motor-control circuit in which the
motor will run when the contactor is manually pressed but will not run
from the control station. The power circuit is energized. What is the
most logical first area to investigate?
A. The motor bearings
B. The control circuit, including the stop/start devices, control
transformer, interlocks, and coil circuit
C. The motor's paint thickness
D. The grounding electrode system
Answer: B.
Rationale: If manually closing the contactor causes the motor to
operate, the power circuit and motor may be capable of functioning.
MECHANIC EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A construction electrical mechanic is preparing to replace a damaged
480-volt, three-phase motor starter. The disconnect supplying the starter
is opened, locked, and tagged. Before touching any conductors, which
procedure provides the most appropriate verification that the circuit is
actually de-energized?
A. Check that the starter's pilot light is extinguished.
B. Use a properly rated voltage tester to test the circuit for absence of
voltage, including phase-to-phase and phase-to-ground as appropriate,
after verifying the tester on a known energized source.
C. Measure resistance between the three phases with an ohmmeter.
D. Press the motor start button and verify that the motor does not rotate.
Answer: B.
Rationale: The absence of a pilot light or motor operation does not
prove that hazardous voltage is absent. A properly rated test
instrument must be used to verify de-energization, and the tester itself
should be verified before and after the test when required by the
applicable electrical-safety procedure. Resistance testing is not an
acceptable substitute for voltage verification on an energized or
potentially energized circuit.
,2.
A 120/208-volt, three-phase, four-wire system supplies several
construction receptacles. A mechanic discovers that one branch circuit
has approximately 208 volts between two ungrounded conductors but
approximately 120 volts from either ungrounded conductor to the
neutral. What does this measurement indicate?
A. The transformer secondary is incorrectly connected.
B. The system is necessarily a 240/120-volt single-phase system.
C. The system is consistent with a 120/208-volt three-phase wye
configuration.
D. The neutral conductor is shorted to the equipment grounding
conductor.
Answer: C.
Rationale: In a typical 120/208-volt wye system, each phase measures
approximately 120 volts to the neutral, while two phase conductors
measure approximately 208 volts from one another. This relationship
results from the 120-degree phase displacement of the three-phase
system.
3.
A mechanic is installing metallic conduit for a 480-volt motor circuit.
The conduit is properly connected at both ends, but a section contains a
poorly installed coupling with significant mechanical damage. Why
should this condition be corrected even if the circuit conductors are
properly insulated?
A. Conduit is used only to provide mechanical protection, so the
coupling has no electrical significance.
B. A damaged coupling can compromise the mechanical integrity and
,continuity of the raceway and may interfere with the effective
grounding/bonding path.
C. The coupling will automatically increase motor current.
D. The damaged coupling will change the motor's phase sequence.
Answer: B.
Rationale: Metallic raceways can form part of the equipment
grounding and bonding path. Damaged or improperly assembled
fittings can compromise both physical protection and electrical
continuity. The condition should be repaired before the installation is
placed into service.
4.
A three-phase motor rotates opposite the desired direction after
installation. The supply voltage and frequency are correct, and the motor
has been inspected for mechanical problems. What is the standard
electrical correction for reversing the rotation of a typical three-phase
induction motor?
A. Reverse the neutral conductor.
B. Swap any two of the three phase conductors supplying the motor.
C. Increase the motor's overload setting.
D. Disconnect the equipment grounding conductor.
Answer: B.
Rationale: Reversing any two phase conductors changes the phase
sequence presented to a three-phase motor and reverses its rotational
direction. The equipment grounding conductor and protective devices
should never be altered as a means of correcting rotation.
5.
, A motor draws substantially higher current than expected immediately
after startup and quickly trips its overload protection. The shaft turns
freely by hand when the motor is disconnected. Which condition should
be investigated first?
A. Incorrect phase sequence only
B. Possible single-phasing, incorrect voltage, winding problems, or an
electrical connection fault
C. Excessive conduit diameter
D. Incorrect color of the grounding conductor
Answer: B.
Rationale: Excessive motor current can result from abnormal supply
voltage, loss of a phase, winding faults, incorrect connections, or
excessive mechanical load. Since the shaft turns freely, electrical
causes deserve immediate attention. Single-phasing is particularly
dangerous because it can produce severe overheating.
6.
A mechanic is troubleshooting a motor-control circuit in which the
motor will run when the contactor is manually pressed but will not run
from the control station. The power circuit is energized. What is the
most logical first area to investigate?
A. The motor bearings
B. The control circuit, including the stop/start devices, control
transformer, interlocks, and coil circuit
C. The motor's paint thickness
D. The grounding electrode system
Answer: B.
Rationale: If manually closing the contactor causes the motor to
operate, the power circuit and motor may be capable of functioning.
