LADWP ELECTRICAL CRAFT HELPER EXAM 2026 NEWEST
EXAM PREPARATION WITH COMPLETE QUESTIONS AND CORRECT
ANSWERS WITH RATIONALES | ALREADY GRADED A+|
|BRAND NEW VERSION!!
SECTION ONE: ELECTRICAL FUNDAMENTALS (Questions 1–50)
Ohm's Law & Basic Electrical Theory
Q1. What is the unit of measurement for electrical resistance?
A) Volt
B) Ampere
C) Ohm
D) Watt
Correct Answer: C) Ohm
Detailed Rationale: Resistance is measured in ohms (Ω). According to Ohm's Law,
resistance (R) is defined as the ratio of voltage (V) to current (I): R = V/I.
One ohm is the resistance value that allows one ampere of current to flow when
one volt is applied. This is a fundamental concept in all electrical work,
especially when sizing conductors, fuses, and circuit breakers.
Q2. Which metal is the best conductor of electricity among common wiring
materials?
A) Aluminum
B) Copper
C) Steel
D) Silver
Correct Answer: B) Copper
Detailed Rationale: Although silver has the highest electrical conductivity of
all metals, it is rarely used in wiring due to cost. Copper is the most common
and practical conductor because it offers excellent conductivity (about 97% of
silver's), good ductility, and reasonable cost. Aluminum is used in some
overhead lines but has lower conductivity and requires special handling. Steel
1
,is a poor conductor and is used for mechanical strength, not electrical
conductivity.
Q3. A circuit has a resistance of 10 ohms and a voltage of 120 volts. What is
the current flowing through the circuit?
A) 0.083 Amperes
B) 12 Amperes
C) 1200 Amperes
D) 1.2 Amperes
Correct Answer: B) 12 Amperes
Detailed Rationale: Ohm's Law states I = V/R. Substituting the given values:
I = 120 V / 10 Ω = 12 A. This calculation is essential for determining whether a
circuit breaker or fuse of the proper rating is needed. A 12-ampere load would
typically require a 15-ampere overcurrent protection device per NEC guidelines.
Q4. A circuit has a resistance of 12 ohms and is supplied by 120 volts. What is
the current flow?
A) 1 Ampere
B) 10 Amperes
C) 12 Amperes
D) 144 Amperes
Correct Answer: B) 10 Amperes
Detailed Rationale: Again using I = V/R: I = 120 V / 12 Ω = 10 A. This is a
straightforward application of Ohm's Law. In the field, you will frequently
calculate current to verify that conductors are not overloaded and that
protective devices are correctly sized.
Q5. What is the formula for electrical power in watts?
A) P = I × R
B) P = V × I
C) P = V × R
2
,D) P = I² × V
Correct Answer: B) P = V × I
Detailed Rationale: The formula for electrical power (P) in a DC circuit is
P = V × I, where V is voltage in volts and I is current in amperes. This is
known as the wattage formula. It is also the basis for the power formula in AC
circuits when power factor is considered. Knowing this allows you to determine
the energy consumption of equipment or the required capacity of transformers
and
generators.
Q6. Two 10-ohm resistors are connected in parallel. What is the total
resistance?
A) 20 ohms
B) 5 ohms
C) 10 ohms
D) 2 ohms
Correct Answer: B) 5 ohms
Detailed Rationale: For two equal resistors in parallel, the total resistance is
half of one resistor's value: R_total = R / n = 10 Ω / 2 = 5 Ω. The general
formula for parallel resistance is 1/R_total = 1/R1 + 1/R2. Parallel circuits
are common in wiring multiple outlets or loads; the total resistance decreases
as more branches are added, increasing total current draw.
Q7. If a 60-watt light bulb operates on 120 volts, what is the current it
draws?
A) 0.5 Amperes
B) 2 Amperes
C) 5 Amperes
D) 0.2 Amperes
Correct Answer: A) 0.5 Amperes
3
, Detailed Rationale: Using P = V × I, we rearrange to I = P/V = 60 W / 120 V =
0.5 A. This is a typical residential lighting load. Understanding this helps in
calculating the total load on a lighting circuit and ensuring it does not exceed
the breaker rating (e.g., a 15-amp breaker can handle up to 1800 watts at 120 V,
but continuous loads should be derated to 80% – 1440 watts – per NEC).
Q8. What is the resistance of a device that draws 2 amperes at 120 volts?
A) 60 ohms
B) 240 ohms
C) 120 ohms
D) 30 ohms
Correct Answer: A) 60 ohms
Detailed Rationale: R = V/I = 120 V / 2 A = 60 Ω. This is an example of
determining the equivalent resistance of a load. In maintenance, you might need
to measure resistance with a multimeter to check if a device is within its
expected range.
Q9. A series circuit has three resistors: 2Ω, 3Ω, and 5Ω. What is the total
resistance?
A) 10Ω
B) 1.2Ω
C) 30Ω
D) 0.5Ω
Correct Answer: A) 10Ω
Detailed Rationale: In a series circuit, total resistance is the sum of
individual resistances: R_total = R1 + R2 + R3 = 2 + 3 + 5 = 10 Ω. This is
critical for understanding voltage drops across each component; the current is
the same through all series elements, but each has a voltage drop proportional
to its resistance.
Q10. In a series circuit, the current is:
4
EXAM PREPARATION WITH COMPLETE QUESTIONS AND CORRECT
ANSWERS WITH RATIONALES | ALREADY GRADED A+|
|BRAND NEW VERSION!!
SECTION ONE: ELECTRICAL FUNDAMENTALS (Questions 1–50)
Ohm's Law & Basic Electrical Theory
Q1. What is the unit of measurement for electrical resistance?
A) Volt
B) Ampere
C) Ohm
D) Watt
Correct Answer: C) Ohm
Detailed Rationale: Resistance is measured in ohms (Ω). According to Ohm's Law,
resistance (R) is defined as the ratio of voltage (V) to current (I): R = V/I.
One ohm is the resistance value that allows one ampere of current to flow when
one volt is applied. This is a fundamental concept in all electrical work,
especially when sizing conductors, fuses, and circuit breakers.
Q2. Which metal is the best conductor of electricity among common wiring
materials?
A) Aluminum
B) Copper
C) Steel
D) Silver
Correct Answer: B) Copper
Detailed Rationale: Although silver has the highest electrical conductivity of
all metals, it is rarely used in wiring due to cost. Copper is the most common
and practical conductor because it offers excellent conductivity (about 97% of
silver's), good ductility, and reasonable cost. Aluminum is used in some
overhead lines but has lower conductivity and requires special handling. Steel
1
,is a poor conductor and is used for mechanical strength, not electrical
conductivity.
Q3. A circuit has a resistance of 10 ohms and a voltage of 120 volts. What is
the current flowing through the circuit?
A) 0.083 Amperes
B) 12 Amperes
C) 1200 Amperes
D) 1.2 Amperes
Correct Answer: B) 12 Amperes
Detailed Rationale: Ohm's Law states I = V/R. Substituting the given values:
I = 120 V / 10 Ω = 12 A. This calculation is essential for determining whether a
circuit breaker or fuse of the proper rating is needed. A 12-ampere load would
typically require a 15-ampere overcurrent protection device per NEC guidelines.
Q4. A circuit has a resistance of 12 ohms and is supplied by 120 volts. What is
the current flow?
A) 1 Ampere
B) 10 Amperes
C) 12 Amperes
D) 144 Amperes
Correct Answer: B) 10 Amperes
Detailed Rationale: Again using I = V/R: I = 120 V / 12 Ω = 10 A. This is a
straightforward application of Ohm's Law. In the field, you will frequently
calculate current to verify that conductors are not overloaded and that
protective devices are correctly sized.
Q5. What is the formula for electrical power in watts?
A) P = I × R
B) P = V × I
C) P = V × R
2
,D) P = I² × V
Correct Answer: B) P = V × I
Detailed Rationale: The formula for electrical power (P) in a DC circuit is
P = V × I, where V is voltage in volts and I is current in amperes. This is
known as the wattage formula. It is also the basis for the power formula in AC
circuits when power factor is considered. Knowing this allows you to determine
the energy consumption of equipment or the required capacity of transformers
and
generators.
Q6. Two 10-ohm resistors are connected in parallel. What is the total
resistance?
A) 20 ohms
B) 5 ohms
C) 10 ohms
D) 2 ohms
Correct Answer: B) 5 ohms
Detailed Rationale: For two equal resistors in parallel, the total resistance is
half of one resistor's value: R_total = R / n = 10 Ω / 2 = 5 Ω. The general
formula for parallel resistance is 1/R_total = 1/R1 + 1/R2. Parallel circuits
are common in wiring multiple outlets or loads; the total resistance decreases
as more branches are added, increasing total current draw.
Q7. If a 60-watt light bulb operates on 120 volts, what is the current it
draws?
A) 0.5 Amperes
B) 2 Amperes
C) 5 Amperes
D) 0.2 Amperes
Correct Answer: A) 0.5 Amperes
3
, Detailed Rationale: Using P = V × I, we rearrange to I = P/V = 60 W / 120 V =
0.5 A. This is a typical residential lighting load. Understanding this helps in
calculating the total load on a lighting circuit and ensuring it does not exceed
the breaker rating (e.g., a 15-amp breaker can handle up to 1800 watts at 120 V,
but continuous loads should be derated to 80% – 1440 watts – per NEC).
Q8. What is the resistance of a device that draws 2 amperes at 120 volts?
A) 60 ohms
B) 240 ohms
C) 120 ohms
D) 30 ohms
Correct Answer: A) 60 ohms
Detailed Rationale: R = V/I = 120 V / 2 A = 60 Ω. This is an example of
determining the equivalent resistance of a load. In maintenance, you might need
to measure resistance with a multimeter to check if a device is within its
expected range.
Q9. A series circuit has three resistors: 2Ω, 3Ω, and 5Ω. What is the total
resistance?
A) 10Ω
B) 1.2Ω
C) 30Ω
D) 0.5Ω
Correct Answer: A) 10Ω
Detailed Rationale: In a series circuit, total resistance is the sum of
individual resistances: R_total = R1 + R2 + R3 = 2 + 3 + 5 = 10 Ω. This is
critical for understanding voltage drops across each component; the current is
the same through all series elements, but each has a voltage drop proportional
to its resistance.
Q10. In a series circuit, the current is:
4
