Indiana Master Electrician Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. A 480V, 3-phase motor draws 52A at full load. What is the approximate kVA
demand?
A. 36.4 kVA
B. 43.3 kVA
C. 38.7 kVA
D. 45.9 kVA
Rationale: kVA for 3-phase is calculated using √3 × V × I ÷ 1000. Substituting
values: 1.732 × 480 × 52 ÷ 1000 ≈ 43.3 kVA. This formula reflects apparent power
in a balanced 3-phase system and is critical for conductor and transformer sizing.
Incorrect options arise from misapplication of single-phase formulas or rounding
errors.
2. The primary purpose of a ground-fault circuit interrupter (GFCI) is to:
A. Protect equipment from overload
B. Increase circuit voltage stability
C. Protect personnel from shock hazards
D. Reduce harmonic distortion
Rationale: GFCIs detect imbalance between hot and neutral conductors, indicating
leakage current through a person or ground. They trip at very low current levels
,(typically 4–6 mA), preventing electrocution. They are not designed for overload or
power quality correction.
3. What is the minimum size copper equipment grounding conductor required
for a 100A circuit using THHN conductors?
A. 10 AWG
B. 12 AWG
C. 8 AWG
D. 6 AWG
Rationale: According to standard NEC grounding tables, a 100A overcurrent device
typically requires an 8 AWG copper grounding conductor. Smaller sizes may not
safely carry fault current long enough for breaker operation.
4. A transformer has a primary of 480V and secondary of 120V with 10 kVA
rating. What is the full-load secondary current?
A. 41.7 A
B. 62.5 A
C. 83.3 A
D. 104.2 A
Rationale: Secondary current = VA ÷ V = 10,000 ÷ 120 = 83.3A. This is fundamental
transformer behavior where power remains constant (minus losses) across
windings.
5. Which conductor material has the highest conductivity?
A. Aluminum
B. Steel
C. Copper
D. Bronze
, Rationale: Copper offers superior electrical conductivity compared to aluminum
and other alloys, making it the standard for most building wiring applications
where performance and thermal characteristics are critical.
6. The maximum voltage drop recommended for branch circuits is typically:
A. 1%
B. 3%
C. 5% total (branch + feeder combined)
D. 10%
Rationale: NEC informational guidelines recommend no more than 3% voltage
drop on branch circuits and 5% total combined. Excessive voltage drop causes
inefficient equipment operation and overheating.
7. A 3-phase load is 12 kW at 0.8 power factor on 208V. What is the current?
A. 33.1 A
B. 41.7 A
C. 52.3 A
D. 60.2 A
Rationale: I = P ÷ (√3 × V × PF) = 12,000 ÷ (1.732 × 208 × 0.8) ≈ 41.7A. Power
factor significantly affects current draw in AC circuits.
8. The purpose of a contactor in motor control is to:
A. Measure current
B. Step down voltage
C. Switch high-current loads using a control circuit
D. Provide overcurrent protection
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. A 480V, 3-phase motor draws 52A at full load. What is the approximate kVA
demand?
A. 36.4 kVA
B. 43.3 kVA
C. 38.7 kVA
D. 45.9 kVA
Rationale: kVA for 3-phase is calculated using √3 × V × I ÷ 1000. Substituting
values: 1.732 × 480 × 52 ÷ 1000 ≈ 43.3 kVA. This formula reflects apparent power
in a balanced 3-phase system and is critical for conductor and transformer sizing.
Incorrect options arise from misapplication of single-phase formulas or rounding
errors.
2. The primary purpose of a ground-fault circuit interrupter (GFCI) is to:
A. Protect equipment from overload
B. Increase circuit voltage stability
C. Protect personnel from shock hazards
D. Reduce harmonic distortion
Rationale: GFCIs detect imbalance between hot and neutral conductors, indicating
leakage current through a person or ground. They trip at very low current levels
,(typically 4–6 mA), preventing electrocution. They are not designed for overload or
power quality correction.
3. What is the minimum size copper equipment grounding conductor required
for a 100A circuit using THHN conductors?
A. 10 AWG
B. 12 AWG
C. 8 AWG
D. 6 AWG
Rationale: According to standard NEC grounding tables, a 100A overcurrent device
typically requires an 8 AWG copper grounding conductor. Smaller sizes may not
safely carry fault current long enough for breaker operation.
4. A transformer has a primary of 480V and secondary of 120V with 10 kVA
rating. What is the full-load secondary current?
A. 41.7 A
B. 62.5 A
C. 83.3 A
D. 104.2 A
Rationale: Secondary current = VA ÷ V = 10,000 ÷ 120 = 83.3A. This is fundamental
transformer behavior where power remains constant (minus losses) across
windings.
5. Which conductor material has the highest conductivity?
A. Aluminum
B. Steel
C. Copper
D. Bronze
, Rationale: Copper offers superior electrical conductivity compared to aluminum
and other alloys, making it the standard for most building wiring applications
where performance and thermal characteristics are critical.
6. The maximum voltage drop recommended for branch circuits is typically:
A. 1%
B. 3%
C. 5% total (branch + feeder combined)
D. 10%
Rationale: NEC informational guidelines recommend no more than 3% voltage
drop on branch circuits and 5% total combined. Excessive voltage drop causes
inefficient equipment operation and overheating.
7. A 3-phase load is 12 kW at 0.8 power factor on 208V. What is the current?
A. 33.1 A
B. 41.7 A
C. 52.3 A
D. 60.2 A
Rationale: I = P ÷ (√3 × V × PF) = 12,000 ÷ (1.732 × 208 × 0.8) ≈ 41.7A. Power
factor significantly affects current draw in AC circuits.
8. The purpose of a contactor in motor control is to:
A. Measure current
B. Step down voltage
C. Switch high-current loads using a control circuit
D. Provide overcurrent protection
