LADWP Electrical Mechanic Exam - Class
Code 3841 Exam Practice Questions and
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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DOMAIN 1 — ELECTRICAL THEORY: DC FUNDAMENTALS
1. Ohm's Law
A 24-volt circuit has a resistance of 6 ohms. What current flows through the
circuit?
A. 2 A
B. 4 A
C. 6 A
D. 144 A
Correct Answer: B. 4 A
Rationale: Ohm's law states that current equals voltage divided by resistance.
Therefore, I = 24 ÷ 6 = 4 amperes.
2. Series Circuit
In a simple series circuit, what happens to the circuit current if one component
becomes an open circuit?
A. Current increases
B. Current remains unchanged
C. Current stops flowing through the series path
D. Voltage becomes zero at the source
Correct Answer: C. Current stops flowing through the series path
,Rationale: A series circuit has a single current path. An open component interrupts
that path, preventing current from flowing through the circuit.
3. Parallel Circuit
What is a fundamental characteristic of components connected in parallel?
A. Each branch is connected across the same two nodes
B. Every branch must have identical resistance
C. Current cannot divide between branches
D. There is only one possible current path
Correct Answer: A. Each branch is connected across the same two nodes
Rationale: Parallel branches share the same two connection points and therefore
have the same voltage across them. Current divides among the available
branches.
4. Electrical Power
A 120-volt load draws 5 amperes. What is its electrical power?
A. 24 W
B. 125 W
C. 600 W
D. 1,200 W
Correct Answer: C. 600 W
Rationale: Electrical power in a DC or resistive circuit can be calculated as P = V × I.
Therefore, 120 × 5 = 600 watts.
5. Resistance
What happens to current in a fixed-voltage circuit when resistance increases?
A. Current increases
B. Current decreases
C. Voltage automatically doubles
D. Power factor becomes unity
Correct Answer: B. Current decreases
,Rationale: According to Ohm's law, current equals voltage divided by resistance.
With voltage held constant, increasing resistance reduces current.
DOMAIN 2 — AC ELECTRICAL THEORY
6. Alternating Current
What distinguishes alternating current from direct current?
A. AC periodically changes direction
B. AC can flow only through batteries
C. AC has no voltage
D. AC cannot produce magnetic fields
Correct Answer: A. AC periodically changes direction
Rationale: Alternating current periodically changes magnitude and direction.
Direct current maintains a substantially constant direction of flow.
7. Frequency
What does the frequency of an AC waveform indicate?
A. Resistance of the circuit
B. Number of cycles occurring per second
C. Maximum conductor temperature
D. Amount of current in amperes
Correct Answer: B. Number of cycles occurring per second
Rationale: Frequency is measured in hertz and represents the number of complete
cycles occurring each second.
8. Transformer Function
What is the primary function of a transformer?
A. Convert AC electrical energy from one voltage level to another through
electromagnetic induction
B. Convert AC directly into mechanical energy without a magnetic field
, C. Store electrical energy permanently
D. Measure conductor resistance
Correct Answer: A. Convert AC electrical energy from one voltage level to
another through electromagnetic induction
Rationale: Transformers transfer AC electrical energy between windings through
electromagnetic induction and can step voltage up or down.
9. Step-Down Transformer
A transformer has more turns on its primary winding than on its secondary
winding. What type of transformer is this?
A. Step-up transformer
B. Isolation-only transformer
C. Step-down transformer
D. Current transformer only
Correct Answer: C. Step-down transformer
Rationale: For an ideal transformer, voltage is proportional to the number of
winding turns. Fewer secondary turns produce a lower secondary voltage.
10. Three-Phase Power
Why are three-phase systems commonly used for industrial motors?
A. They provide efficient power transmission and smooth motor operation
B. They eliminate the need for conductors
C. They operate only on batteries
D. They cannot produce rotating magnetic fields
Correct Answer: A. They provide efficient power transmission and smooth
motor operation
Rationale: Three-phase systems provide efficient power delivery and naturally
produce a rotating magnetic field suitable for operating three-phase motors.
DOMAIN 3 — ELECTRICAL MEASUREMENT AND METERS
Code 3841 Exam Practice Questions and
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
DOMAIN 1 — ELECTRICAL THEORY: DC FUNDAMENTALS
1. Ohm's Law
A 24-volt circuit has a resistance of 6 ohms. What current flows through the
circuit?
A. 2 A
B. 4 A
C. 6 A
D. 144 A
Correct Answer: B. 4 A
Rationale: Ohm's law states that current equals voltage divided by resistance.
Therefore, I = 24 ÷ 6 = 4 amperes.
2. Series Circuit
In a simple series circuit, what happens to the circuit current if one component
becomes an open circuit?
A. Current increases
B. Current remains unchanged
C. Current stops flowing through the series path
D. Voltage becomes zero at the source
Correct Answer: C. Current stops flowing through the series path
,Rationale: A series circuit has a single current path. An open component interrupts
that path, preventing current from flowing through the circuit.
3. Parallel Circuit
What is a fundamental characteristic of components connected in parallel?
A. Each branch is connected across the same two nodes
B. Every branch must have identical resistance
C. Current cannot divide between branches
D. There is only one possible current path
Correct Answer: A. Each branch is connected across the same two nodes
Rationale: Parallel branches share the same two connection points and therefore
have the same voltage across them. Current divides among the available
branches.
4. Electrical Power
A 120-volt load draws 5 amperes. What is its electrical power?
A. 24 W
B. 125 W
C. 600 W
D. 1,200 W
Correct Answer: C. 600 W
Rationale: Electrical power in a DC or resistive circuit can be calculated as P = V × I.
Therefore, 120 × 5 = 600 watts.
5. Resistance
What happens to current in a fixed-voltage circuit when resistance increases?
A. Current increases
B. Current decreases
C. Voltage automatically doubles
D. Power factor becomes unity
Correct Answer: B. Current decreases
,Rationale: According to Ohm's law, current equals voltage divided by resistance.
With voltage held constant, increasing resistance reduces current.
DOMAIN 2 — AC ELECTRICAL THEORY
6. Alternating Current
What distinguishes alternating current from direct current?
A. AC periodically changes direction
B. AC can flow only through batteries
C. AC has no voltage
D. AC cannot produce magnetic fields
Correct Answer: A. AC periodically changes direction
Rationale: Alternating current periodically changes magnitude and direction.
Direct current maintains a substantially constant direction of flow.
7. Frequency
What does the frequency of an AC waveform indicate?
A. Resistance of the circuit
B. Number of cycles occurring per second
C. Maximum conductor temperature
D. Amount of current in amperes
Correct Answer: B. Number of cycles occurring per second
Rationale: Frequency is measured in hertz and represents the number of complete
cycles occurring each second.
8. Transformer Function
What is the primary function of a transformer?
A. Convert AC electrical energy from one voltage level to another through
electromagnetic induction
B. Convert AC directly into mechanical energy without a magnetic field
, C. Store electrical energy permanently
D. Measure conductor resistance
Correct Answer: A. Convert AC electrical energy from one voltage level to
another through electromagnetic induction
Rationale: Transformers transfer AC electrical energy between windings through
electromagnetic induction and can step voltage up or down.
9. Step-Down Transformer
A transformer has more turns on its primary winding than on its secondary
winding. What type of transformer is this?
A. Step-up transformer
B. Isolation-only transformer
C. Step-down transformer
D. Current transformer only
Correct Answer: C. Step-down transformer
Rationale: For an ideal transformer, voltage is proportional to the number of
winding turns. Fewer secondary turns produce a lower secondary voltage.
10. Three-Phase Power
Why are three-phase systems commonly used for industrial motors?
A. They provide efficient power transmission and smooth motor operation
B. They eliminate the need for conductors
C. They operate only on batteries
D. They cannot produce rotating magnetic fields
Correct Answer: A. They provide efficient power transmission and smooth
motor operation
Rationale: Three-phase systems provide efficient power delivery and naturally
produce a rotating magnetic field suitable for operating three-phase motors.
DOMAIN 3 — ELECTRICAL MEASUREMENT AND METERS
