NASCLA National Electrical Contractor
Exam (Alabama Candidate) – Mock Test
and Study Guide
SECTION A: ELECTRICAL THEORY & PRINCIPLES
1. Which law states that the sum of currents entering a junction equals the sum
of currents leaving the junction?
• A) Ohm's Law
• B) Kirchhoff's Current Law
• C) Faraday's Law
• D) The Power Law
Answer: B) Kirchhoff's Current Law
Rationale: Kirchhoff's Current Law (KCL) governs the conservation of electric
charge at a node. This is a fundamental principle tested on the NASCLA electrical
exam .
2. In a purely resistive DC circuit, if the voltage is doubled while resistance
remains constant, the power consumed will:
• A) Remain the same
• B) Double
• C) Quadruple
• D) Halve
,Answer: C) Quadruple
Rationale: Power P = V²/R. Doubling V causes P to increase by a factor of four. This
is a common theory question .
3. For a three-phase, four-wire wye system, the line-to-neutral voltage is 120 V.
What is the line-to-line voltage?
• A) 120 V
• B) 208 V
• C) 240 V
• D) 277 V
Answer: B) 208 V
Rationale: In a wye system, V_line = √3 × V_phase. Thus, 120 V × √3 ≈ 208 V. This is
a critical NEC-related calculation .
4. A motor rated 5 kW, 230 V, 3-phase, with a power factor of 0.9. What is its
full-load current?
• A) 10.9 A
• B) 12.4 A
• C) 14.0 A
• D) 15.5 A
Answer: C) 14.0 A
Rationale: I = P ÷ (√3 × V × PF) = 5000 ÷ (1.732 × 230 × 0.9) ≈ 14 A .
5. What is the reactance of an inductor at 60 Hz if its inductance is 1.33 mH?
• A) 0.25 Ω
, • B) 0.50 Ω
• C) 0.75 Ω
• D) 1.00 Ω
Answer: B) 0.50 Ω
Rationale: XL = 2πfL = 2π × 60 × 0.00133 ≈ 0.5 Ω .
6. Which type of electrical current is commonly used in residential and
commercial power distribution?
• A) Direct Current (DC)
• B) Alternating Current (AC)
• C) Pulsating DC
• D) Static Electricity
Answer: B) Alternating Current (AC)
Rationale: AC is the standard for power distribution because it can be efficiently
transformed to different voltages.
7. The opposition to current flow in an AC circuit that is caused by capacitance is
called:
• A) Inductive reactance
• B) Capacitive reactance
• C) Impedance
• D) Resistance
Answer: B) Capacitive reactance
Rationale: Capacitive reactance is the opposition to AC current flow caused by
capacitance, measured in ohms.
, 8. A conductor with a cross-sectional area of 4/0 AWG has a diameter
approximately equal to:
• A) 0.46 inches
• B) 0.52 inches
• C) 0.58 inches
• D) 0.64 inches
Answer: A) 0.46 inches
Rationale: 4/0 AWG is one of the largest standard wire sizes, with a diameter of
approximately 0.46 inches.
9. The power in a single-phase AC circuit is calculated using which formula?
• A) P = V × I
• B) P = V × I × PF
• C) P = V × I × √3
• D) P = V × I × PF × √3
Answer: B) P = V × I × PF
Rationale: Single-phase AC power equals voltage times current times power factor
(PF).
10. A 1,800-watt lighting circuit at 120 V draws how many amps?
• A) 10 A
• B) 12 A
• C) 15 A
• D) 20 A
Exam (Alabama Candidate) – Mock Test
and Study Guide
SECTION A: ELECTRICAL THEORY & PRINCIPLES
1. Which law states that the sum of currents entering a junction equals the sum
of currents leaving the junction?
• A) Ohm's Law
• B) Kirchhoff's Current Law
• C) Faraday's Law
• D) The Power Law
Answer: B) Kirchhoff's Current Law
Rationale: Kirchhoff's Current Law (KCL) governs the conservation of electric
charge at a node. This is a fundamental principle tested on the NASCLA electrical
exam .
2. In a purely resistive DC circuit, if the voltage is doubled while resistance
remains constant, the power consumed will:
• A) Remain the same
• B) Double
• C) Quadruple
• D) Halve
,Answer: C) Quadruple
Rationale: Power P = V²/R. Doubling V causes P to increase by a factor of four. This
is a common theory question .
3. For a three-phase, four-wire wye system, the line-to-neutral voltage is 120 V.
What is the line-to-line voltage?
• A) 120 V
• B) 208 V
• C) 240 V
• D) 277 V
Answer: B) 208 V
Rationale: In a wye system, V_line = √3 × V_phase. Thus, 120 V × √3 ≈ 208 V. This is
a critical NEC-related calculation .
4. A motor rated 5 kW, 230 V, 3-phase, with a power factor of 0.9. What is its
full-load current?
• A) 10.9 A
• B) 12.4 A
• C) 14.0 A
• D) 15.5 A
Answer: C) 14.0 A
Rationale: I = P ÷ (√3 × V × PF) = 5000 ÷ (1.732 × 230 × 0.9) ≈ 14 A .
5. What is the reactance of an inductor at 60 Hz if its inductance is 1.33 mH?
• A) 0.25 Ω
, • B) 0.50 Ω
• C) 0.75 Ω
• D) 1.00 Ω
Answer: B) 0.50 Ω
Rationale: XL = 2πfL = 2π × 60 × 0.00133 ≈ 0.5 Ω .
6. Which type of electrical current is commonly used in residential and
commercial power distribution?
• A) Direct Current (DC)
• B) Alternating Current (AC)
• C) Pulsating DC
• D) Static Electricity
Answer: B) Alternating Current (AC)
Rationale: AC is the standard for power distribution because it can be efficiently
transformed to different voltages.
7. The opposition to current flow in an AC circuit that is caused by capacitance is
called:
• A) Inductive reactance
• B) Capacitive reactance
• C) Impedance
• D) Resistance
Answer: B) Capacitive reactance
Rationale: Capacitive reactance is the opposition to AC current flow caused by
capacitance, measured in ohms.
, 8. A conductor with a cross-sectional area of 4/0 AWG has a diameter
approximately equal to:
• A) 0.46 inches
• B) 0.52 inches
• C) 0.58 inches
• D) 0.64 inches
Answer: A) 0.46 inches
Rationale: 4/0 AWG is one of the largest standard wire sizes, with a diameter of
approximately 0.46 inches.
9. The power in a single-phase AC circuit is calculated using which formula?
• A) P = V × I
• B) P = V × I × PF
• C) P = V × I × √3
• D) P = V × I × PF × √3
Answer: B) P = V × I × PF
Rationale: Single-phase AC power equals voltage times current times power factor
(PF).
10. A 1,800-watt lighting circuit at 120 V draws how many amps?
• A) 10 A
• B) 12 A
• C) 15 A
• D) 20 A
