LADWP ELECTRICAL CRAFT HELPER EXAM 2026
PRACTICE QUESTIONS, VERIFIED ANSWERS &
DETAILED RATIONALES
SECTION 1: BASIC ELECTRICAL THEORY (DC & AC)
1. What is the standard unit of measurement for electrical resistance?
A) Ampere
B) Volt
C) Ohm
D) Watt
Answer: C) Ohm
Rationale: The Ohm is the SI unit of electrical resistance, symbolized by the Greek letter
omega (Ω). Amperes measure current, Volts measure potential difference, and Watts
measure power.
2. A circuit has a voltage of 120V and a resistance of 30Ω. What is the current?
A) 0.25 A
B) 4 A
C) 3600 A
D) 150 A
Answer: B) 4 A
Rationale: Using Ohm's Law: I = V / R = 120V / 30Ω = 4 Amperes.
3. What is the total resistance of two 10Ω resistors connected in series?
A) 5 Ω
B) 10 Ω
C) 15 Ω
,D) 20 Ω
Answer: D) 20 Ω
Rationale: In a series circuit, resistances add together. R_total = R1 + R2 = 10Ω + 10Ω =
20Ω.
4. In a parallel circuit, the voltage across each branch is:
A) Divided equally.
B) The same as the source voltage.
C) Reduced by the resistance of the branch.
D) Doubled.
Answer: B) The same as the source voltage.
Rationale: In a parallel circuit, all components share the same two nodes; therefore, the
voltage drop across each branch is equal to the source voltage.
5. A material that allows electrons to flow easily is known as a:
A) Insulator
B) Conductor
C) Resistor
D) Semiconductor
Answer: B) Conductor
Rationale: Conductors (like copper and aluminum) have free electrons that allow
electric current to flow easily. Insulators restrict flow.
6. What is the power dissipated by a 10Ω resistor carrying 5 Amperes?
A) 50 Watts
B) 2 Watts
C) 250 Watts
D) 0.5 Watts
Answer: C) 250 Watts
Rationale: Power formula: P = I² * R = (5²) * 10 = 25 * 10 = 250 Watts.
,7. Alternating Current (AC) differs from Direct Current (DC) because AC:
A) Flows in only one direction.
B) Has a higher voltage.
C) Reverses direction periodically.
D) Cannot be measured.
Answer: C) Reverses direction periodically.
Rationale: AC changes polarity and magnitude over time (typically in a sine wave),
while DC flows steadily in one direction.
8. The standard frequency of AC power in the United States is:
A) 50 Hz
B) 60 Hz
C) 100 Hz
D) 400 Hz
Answer: B) 60 Hz
Rationale: The North American power grid standard is 60 Hertz (cycles per second).
Europe uses 50 Hz.
9. What does a transformer do?
A) Converts AC to DC.
B) Increases or decreases voltage.
C) Stores electrical charge.
D) Measures current flow.
Answer: B) Increases or decreases voltage.
Rationale: A transformer uses electromagnetic induction to step up (increase) or step
down (decrease) AC voltage while maintaining frequency.
10. The "hot" wire in a standard 120V residential circuit is usually what color?
A) White
, B) Green
C) Black or Red
D) Bare Copper
Answer: C) Black or Red
Rationale: In US wiring, black and red are typically used for ungrounded (hot)
conductors. White is neutral, and green/bare is ground.
11. A ground fault is best described as:
A) An open circuit.
B) A short circuit to the earth or grounding system.
C) An overloaded neutral wire.
D) High resistance in a wire.
Answer: B) A short circuit to the earth or grounding system.
Rationale: A ground fault occurs when electricity takes an unintended path to the
ground (earth), which can be dangerous.
12. What is capacitance?
A) The ability to store electrical charge.
B) The opposition to current flow.
C) The rate of electron flow.
D) The force pushing electrons.
Answer: A) The ability to store electrical charge.
Rationale: Capacitance is the property of a capacitor to store an electrical charge in
an electrostatic field.
13. In a DC circuit, an inductor acts like a:
A) Short circuit (low resistance) after a long time.
B) Open circuit (high resistance) after a long time.
C) Battery.
D) Capacitor.
PRACTICE QUESTIONS, VERIFIED ANSWERS &
DETAILED RATIONALES
SECTION 1: BASIC ELECTRICAL THEORY (DC & AC)
1. What is the standard unit of measurement for electrical resistance?
A) Ampere
B) Volt
C) Ohm
D) Watt
Answer: C) Ohm
Rationale: The Ohm is the SI unit of electrical resistance, symbolized by the Greek letter
omega (Ω). Amperes measure current, Volts measure potential difference, and Watts
measure power.
2. A circuit has a voltage of 120V and a resistance of 30Ω. What is the current?
A) 0.25 A
B) 4 A
C) 3600 A
D) 150 A
Answer: B) 4 A
Rationale: Using Ohm's Law: I = V / R = 120V / 30Ω = 4 Amperes.
3. What is the total resistance of two 10Ω resistors connected in series?
A) 5 Ω
B) 10 Ω
C) 15 Ω
,D) 20 Ω
Answer: D) 20 Ω
Rationale: In a series circuit, resistances add together. R_total = R1 + R2 = 10Ω + 10Ω =
20Ω.
4. In a parallel circuit, the voltage across each branch is:
A) Divided equally.
B) The same as the source voltage.
C) Reduced by the resistance of the branch.
D) Doubled.
Answer: B) The same as the source voltage.
Rationale: In a parallel circuit, all components share the same two nodes; therefore, the
voltage drop across each branch is equal to the source voltage.
5. A material that allows electrons to flow easily is known as a:
A) Insulator
B) Conductor
C) Resistor
D) Semiconductor
Answer: B) Conductor
Rationale: Conductors (like copper and aluminum) have free electrons that allow
electric current to flow easily. Insulators restrict flow.
6. What is the power dissipated by a 10Ω resistor carrying 5 Amperes?
A) 50 Watts
B) 2 Watts
C) 250 Watts
D) 0.5 Watts
Answer: C) 250 Watts
Rationale: Power formula: P = I² * R = (5²) * 10 = 25 * 10 = 250 Watts.
,7. Alternating Current (AC) differs from Direct Current (DC) because AC:
A) Flows in only one direction.
B) Has a higher voltage.
C) Reverses direction periodically.
D) Cannot be measured.
Answer: C) Reverses direction periodically.
Rationale: AC changes polarity and magnitude over time (typically in a sine wave),
while DC flows steadily in one direction.
8. The standard frequency of AC power in the United States is:
A) 50 Hz
B) 60 Hz
C) 100 Hz
D) 400 Hz
Answer: B) 60 Hz
Rationale: The North American power grid standard is 60 Hertz (cycles per second).
Europe uses 50 Hz.
9. What does a transformer do?
A) Converts AC to DC.
B) Increases or decreases voltage.
C) Stores electrical charge.
D) Measures current flow.
Answer: B) Increases or decreases voltage.
Rationale: A transformer uses electromagnetic induction to step up (increase) or step
down (decrease) AC voltage while maintaining frequency.
10. The "hot" wire in a standard 120V residential circuit is usually what color?
A) White
, B) Green
C) Black or Red
D) Bare Copper
Answer: C) Black or Red
Rationale: In US wiring, black and red are typically used for ungrounded (hot)
conductors. White is neutral, and green/bare is ground.
11. A ground fault is best described as:
A) An open circuit.
B) A short circuit to the earth or grounding system.
C) An overloaded neutral wire.
D) High resistance in a wire.
Answer: B) A short circuit to the earth or grounding system.
Rationale: A ground fault occurs when electricity takes an unintended path to the
ground (earth), which can be dangerous.
12. What is capacitance?
A) The ability to store electrical charge.
B) The opposition to current flow.
C) The rate of electron flow.
D) The force pushing electrons.
Answer: A) The ability to store electrical charge.
Rationale: Capacitance is the property of a capacitor to store an electrical charge in
an electrostatic field.
13. In a DC circuit, an inductor acts like a:
A) Short circuit (low resistance) after a long time.
B) Open circuit (high resistance) after a long time.
C) Battery.
D) Capacitor.
