EETC Electrical Safety & Code Compliance 4 — Questions and Answers
Question 1: In a 3-phase 4-wire wye system, what voltage exists between any two hot conductors?
- 120V
- 208V (Correct answer)
- 240V
- 277V
Correct answer: 208V
In a 208Y/120V wye system, line-to-line voltage is 120V × √3 ≈ 208V between any two phase conductors.
Question 2: Which NEC article governs the installation of branch circuits?
- Article 200
- Article 210 (Correct answer)
- Article 220
- Article 230
Correct answer: Article 210
NEC Article 210 covers branch circuits, including ratings, required outlets, and GFCI/AFCI requirements.
Question 3: An AFCI breaker is designed primarily to protect against which type of hazard?
- Ground faults causing electrocution
- Arcing faults that can ignite fires (Correct answer)
- Overcurrent conditions
- Voltage surges from lightning
Correct answer: Arcing faults that can ignite fires
Arc Fault Circuit Interrupters detect the unique electrical signature of dangerous arcing faults that can ignite fires without tripping standard breakers.
Question 4: What is the maximum voltage drop allowed on a branch circuit per NEC recommended practice (informational note)?
- 1%
- 3% (Correct answer)
- 5%
- 7%
Correct answer: 3%
NEC 210.19(A) informational note recommends limiting branch circuit voltage drop to 3% for best performance.
Question 5: A worker must use rubber insulating gloves rated for 1,000V. According to ASTM standards, what class are these gloves?
- Class 00
- Class 0 (Correct answer)
- Class 1
- Class 2
Correct answer: Class 0
ASTM Class 0 rubber insulating gloves are rated for maximum use voltage of 1,000V AC (1,500V DC).
Question 6: Under NEC 300.5, the minimum burial depth for a 120V residential circuit in a rigid metal conduit (RMC) is:
- 6 inches (Correct answer)
- 12 inches
- 18 inches
- 24 inches
Correct answer: 6 inches
NEC Table 300.5 allows only 6 inches of cover for circuits in rigid metal conduit due to its superior mechanical protection.
Question 7: Which document defines the national minimum safety standard for electrical installations in the United States?
- OSHA 29 CFR 1910
- NFPA 70 (National Electrical Code) (Correct answer)
- ANSI C2 (NESC)
- IEEE 1584
Correct answer: NFPA 70 (National Electrical Code)
NFPA 70, the National Electrical Code (NEC), is the nationally recognized minimum safety standard for electrical installations in the US.
EETC Electrical Safety & Code Compliance 4
In a 3-phase 4-wire wye system, what voltage exists between any two hot conductors?