LADWP Electrical Mechanic Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. An Electrical Mechanic is troubleshooting a 240-volt electric heater
that is rated at 4,800 watts. Before energizing the circuit, the
mechanic disconnects power and measures the resistance of the
heating element. Based on the nameplate information, what
resistance value should be expected if the heater is operating
correctly?
A. 6 Ω
B. 12 Ω
C. 24 Ω
D. 48 Ω
Rationale: Using the power formula P = V²/R, resistance equals V²/P.
Therefore, R = 240² ÷ 4,800 = 57,600 ÷ 4,800 = 12 ohms. This type of power
,calculation is commonly tested in electrical mechanic examinations
involving Ohm’s Law and electrical theory.
2. A conductor carries a current of 15 amperes when connected to a 120-
volt source. Assuming resistance remains constant, what is the
resistance of the conductor?
A. 4 Ω
B. 8 Ω
C. 12 Ω
D. 18 Ω
Rationale: Ohm's Law states that resistance equals voltage divided by
current. Therefore, R = 120 ÷ 15 = 8 ohms. Electrical mechanics must
routinely apply Ohm's Law during troubleshooting and testing activities.
3. When using a megger during preventive maintenance of a motor, the
primary purpose of the instrument is to measure:
A. Current flow
B. Voltage drop
C. Power factor
D. Insulation resistance
,Rationale: A megger is specifically designed to test insulation resistance by
applying a high test voltage and measuring leakage current. It is
commonly used on motors, feeders, transformers, and cable systems.
4. In a series circuit containing three resistors of 5 Ω, 10 Ω, and 15 Ω,
what is the total circuit resistance?
A. 10 Ω
B. 15 Ω
C. 20 Ω
D. 30 Ω
Rationale: Resistances in a series circuit add directly. Therefore, total
resistance equals 5 + 10 + 15 = 30 ohms. Understanding series and parallel
circuit calculations is essential for electrical maintenance work.
5. An electrician measures 480 volts across a motor drawing 25 amperes.
Assuming unity power factor for simplicity, approximately how much
electrical power is being consumed?
A. 6,000 W
B. 9,600 W
C. 12,000 W
D. 18,000 W
, Rationale: Electrical power is calculated using P = V × I. Therefore, P = 480
× 25 = 12,000 watts. Power calculations are frequently encountered during
equipment troubleshooting and load analysis.
6. Which device is primarily used to measure electrical current flowing
through a circuit?
A. Voltmeter
B. Ohmmeter
C. Wattmeter
D. Ammeter
Rationale: An ammeter is designed specifically to measure current flow in
amperes. Proper instrument selection is a fundamental skill for electrical
mechanics.
7. A transformer has 1,000 turns on the primary winding and 250 turns
on the secondary winding. If the primary voltage is 480 volts, what
secondary voltage should be expected?
A. 60 V
B. 120 V
C. 240 V
D. 960 V
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. An Electrical Mechanic is troubleshooting a 240-volt electric heater
that is rated at 4,800 watts. Before energizing the circuit, the
mechanic disconnects power and measures the resistance of the
heating element. Based on the nameplate information, what
resistance value should be expected if the heater is operating
correctly?
A. 6 Ω
B. 12 Ω
C. 24 Ω
D. 48 Ω
Rationale: Using the power formula P = V²/R, resistance equals V²/P.
Therefore, R = 240² ÷ 4,800 = 57,600 ÷ 4,800 = 12 ohms. This type of power
,calculation is commonly tested in electrical mechanic examinations
involving Ohm’s Law and electrical theory.
2. A conductor carries a current of 15 amperes when connected to a 120-
volt source. Assuming resistance remains constant, what is the
resistance of the conductor?
A. 4 Ω
B. 8 Ω
C. 12 Ω
D. 18 Ω
Rationale: Ohm's Law states that resistance equals voltage divided by
current. Therefore, R = 120 ÷ 15 = 8 ohms. Electrical mechanics must
routinely apply Ohm's Law during troubleshooting and testing activities.
3. When using a megger during preventive maintenance of a motor, the
primary purpose of the instrument is to measure:
A. Current flow
B. Voltage drop
C. Power factor
D. Insulation resistance
,Rationale: A megger is specifically designed to test insulation resistance by
applying a high test voltage and measuring leakage current. It is
commonly used on motors, feeders, transformers, and cable systems.
4. In a series circuit containing three resistors of 5 Ω, 10 Ω, and 15 Ω,
what is the total circuit resistance?
A. 10 Ω
B. 15 Ω
C. 20 Ω
D. 30 Ω
Rationale: Resistances in a series circuit add directly. Therefore, total
resistance equals 5 + 10 + 15 = 30 ohms. Understanding series and parallel
circuit calculations is essential for electrical maintenance work.
5. An electrician measures 480 volts across a motor drawing 25 amperes.
Assuming unity power factor for simplicity, approximately how much
electrical power is being consumed?
A. 6,000 W
B. 9,600 W
C. 12,000 W
D. 18,000 W
, Rationale: Electrical power is calculated using P = V × I. Therefore, P = 480
× 25 = 12,000 watts. Power calculations are frequently encountered during
equipment troubleshooting and load analysis.
6. Which device is primarily used to measure electrical current flowing
through a circuit?
A. Voltmeter
B. Ohmmeter
C. Wattmeter
D. Ammeter
Rationale: An ammeter is designed specifically to measure current flow in
amperes. Proper instrument selection is a fundamental skill for electrical
mechanics.
7. A transformer has 1,000 turns on the primary winding and 250 turns
on the secondary winding. If the primary voltage is 480 volts, what
secondary voltage should be expected?
A. 60 V
B. 120 V
C. 240 V
D. 960 V
