LADWP ELECTRIC DISTRIBUTION
MECHANIC TRAINEE PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. Electrical Fundamentals
A distribution mechanic trainee is troubleshooting a circuit supplied by a
120-volt source. The circuit contains a resistance of 30 ohms. Assuming
the circuit is purely resistive and there are no other significant losses,
approximately how much current should the mechanic expect to
measure?
A. 0.25 A
B. 2 A
C. 4 A
D. 30 A
Answer: C. 4 A
Rationale: Ohm's law states that current equals voltage divided by
resistance: I = V/R. Therefore, I = 120 V ÷ 30 Ω = 4 A. The 0.25-A
answer results from reversing the relationship, while 30 A incorrectly
treats resistance as current. Understanding the relationship between
voltage, current, and resistance is fundamental when troubleshooting
distribution equipment and circuits.
2. Series Circuits
1
,Two resistors, 10 ohms and 20 ohms, are connected in series across a
120-volt source. What is the total resistance?
A. 5 Ω
B. 20 Ω
C. 30 Ω
D. 200 Ω
Answer: C. 30 Ω
Rationale: Resistors connected in series are added directly: Rtotal =
R1 + R2. Thus, 10 Ω + 20 Ω = 30 Ω. Series resistance increases the
overall opposition to current flow. A trainee should recognize this
relationship when analyzing control circuits, test circuits, and other
electrical assemblies.
3. Parallel Circuits
Two 20-ohm resistors are connected in parallel. What is their equivalent
resistance?
A. 10 Ω
B. 20 Ω
C. 40 Ω
D. 400 Ω
Answer: A. 10 Ω
Rationale: For two equal resistors in parallel, the equivalent resistance
is one-half the value of either resistor. Therefore, 20 Ω ÷ 2 = 10 Ω.
Parallel circuits provide multiple current paths, so their equivalent
resistance is lower than the resistance of any individual branch.
4. Electrical Power
2
,A 240-volt heater draws 10 amperes. Approximately how much
electrical power does it consume?
A. 24 W
B. 240 W
C. 1,200 W
D. 2,400 W
Answer: D. 2,400 W
Rationale: For a simple resistive load, electrical power is calculated as
P = V × I. Therefore, 240 V × 10 A = 2,400 W, or 2.4 kW. Power
calculations help mechanics understand equipment loading, conductor
requirements, and the amount of electrical energy converted into heat
or mechanical work.
5. AC Versus DC
Which statement most accurately describes alternating current?
A. It always flows in only one direction.
B. Its magnitude and direction periodically change.
C. It cannot be transformed to another voltage.
D. It can only be produced by batteries.
Answer: B. Its magnitude and direction periodically change.
Rationale: Alternating current periodically reverses direction and
generally varies in magnitude according to the waveform. Utility
distribution systems predominantly use AC because AC voltage can be
efficiently transformed to different voltage levels using transformers.
Batteries, by contrast, normally provide direct current.
6. Conductor Resistance
3
, Which condition generally causes the resistance of a metallic conductor
to increase?
A. Decreasing its temperature
B. Increasing its temperature
C. Increasing its insulation thickness
D. Reducing the surrounding air pressure
Answer: B. Increasing its temperature
Rationale: For most metallic conductors, resistance increases as
temperature rises. Increased resistance can produce additional voltage
drop and heating, creating a potentially undesirable feedback
condition under heavy loading. This is why conductor ampacity and
equipment operating temperature are important considerations in
electrical distribution work.
7. Voltage Measurement
When measuring voltage across a component in a properly energized
circuit, a voltmeter should generally be connected:
A. In series with the component
B. In parallel with the component
C. Between two points on the same wire only
D. Directly across a current transformer secondary without regard to its
circuit
Answer: B. In parallel with the component
Rationale: Voltage is the electrical potential difference between two
points, so a voltmeter measures that difference by connecting across
the two points. An ammeter, by contrast, is normally inserted in series
so the circuit current passes through it. Incorrectly connecting a
conventional voltmeter in series can produce incorrect measurements
and potentially create a hazardous condition.
4
MECHANIC TRAINEE PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. Electrical Fundamentals
A distribution mechanic trainee is troubleshooting a circuit supplied by a
120-volt source. The circuit contains a resistance of 30 ohms. Assuming
the circuit is purely resistive and there are no other significant losses,
approximately how much current should the mechanic expect to
measure?
A. 0.25 A
B. 2 A
C. 4 A
D. 30 A
Answer: C. 4 A
Rationale: Ohm's law states that current equals voltage divided by
resistance: I = V/R. Therefore, I = 120 V ÷ 30 Ω = 4 A. The 0.25-A
answer results from reversing the relationship, while 30 A incorrectly
treats resistance as current. Understanding the relationship between
voltage, current, and resistance is fundamental when troubleshooting
distribution equipment and circuits.
2. Series Circuits
1
,Two resistors, 10 ohms and 20 ohms, are connected in series across a
120-volt source. What is the total resistance?
A. 5 Ω
B. 20 Ω
C. 30 Ω
D. 200 Ω
Answer: C. 30 Ω
Rationale: Resistors connected in series are added directly: Rtotal =
R1 + R2. Thus, 10 Ω + 20 Ω = 30 Ω. Series resistance increases the
overall opposition to current flow. A trainee should recognize this
relationship when analyzing control circuits, test circuits, and other
electrical assemblies.
3. Parallel Circuits
Two 20-ohm resistors are connected in parallel. What is their equivalent
resistance?
A. 10 Ω
B. 20 Ω
C. 40 Ω
D. 400 Ω
Answer: A. 10 Ω
Rationale: For two equal resistors in parallel, the equivalent resistance
is one-half the value of either resistor. Therefore, 20 Ω ÷ 2 = 10 Ω.
Parallel circuits provide multiple current paths, so their equivalent
resistance is lower than the resistance of any individual branch.
4. Electrical Power
2
,A 240-volt heater draws 10 amperes. Approximately how much
electrical power does it consume?
A. 24 W
B. 240 W
C. 1,200 W
D. 2,400 W
Answer: D. 2,400 W
Rationale: For a simple resistive load, electrical power is calculated as
P = V × I. Therefore, 240 V × 10 A = 2,400 W, or 2.4 kW. Power
calculations help mechanics understand equipment loading, conductor
requirements, and the amount of electrical energy converted into heat
or mechanical work.
5. AC Versus DC
Which statement most accurately describes alternating current?
A. It always flows in only one direction.
B. Its magnitude and direction periodically change.
C. It cannot be transformed to another voltage.
D. It can only be produced by batteries.
Answer: B. Its magnitude and direction periodically change.
Rationale: Alternating current periodically reverses direction and
generally varies in magnitude according to the waveform. Utility
distribution systems predominantly use AC because AC voltage can be
efficiently transformed to different voltage levels using transformers.
Batteries, by contrast, normally provide direct current.
6. Conductor Resistance
3
, Which condition generally causes the resistance of a metallic conductor
to increase?
A. Decreasing its temperature
B. Increasing its temperature
C. Increasing its insulation thickness
D. Reducing the surrounding air pressure
Answer: B. Increasing its temperature
Rationale: For most metallic conductors, resistance increases as
temperature rises. Increased resistance can produce additional voltage
drop and heating, creating a potentially undesirable feedback
condition under heavy loading. This is why conductor ampacity and
equipment operating temperature are important considerations in
electrical distribution work.
7. Voltage Measurement
When measuring voltage across a component in a properly energized
circuit, a voltmeter should generally be connected:
A. In series with the component
B. In parallel with the component
C. Between two points on the same wire only
D. Directly across a current transformer secondary without regard to its
circuit
Answer: B. In parallel with the component
Rationale: Voltage is the electrical potential difference between two
points, so a voltmeter measures that difference by connecting across
the two points. An ammeter, by contrast, is normally inserted in series
so the circuit current passes through it. Incorrectly connecting a
conventional voltmeter in series can produce incorrect measurements
and potentially create a hazardous condition.
4
