ETC ETC Electrical & Electronic Systems 1 — Questions and Answers
Question 1: What is the standard US residential single-phase voltage supplied to most homes?
- 120/240 V (Correct answer)
- 208/480 V
- 277/480 V
- 120/208 V
Correct answer: 120/240 V
US residential service is single-phase 120/240 V, providing 120 V for general outlets and 240 V for large appliances.
Question 2: Which electrical code governs the installation of electrical wiring and equipment in the United States?
- NFPA 70 (NEC) (Correct answer)
- OSHA 29 CFR 1910
- IEEE 519
- ANSI C84.1
Correct answer: NFPA 70 (NEC)
NFPA 70, the National Electrical Code (NEC), is the primary standard for safe electrical installation in the US.
Question 3: In Ohm's Law, if a circuit has a voltage of 120 V and a resistance of 60 ohms, what is the current?
- 2 A (Correct answer)
- 0.5 A
- 7200 A
- 60 A
Correct answer: 2 A
Ohm's Law states I = V/R; 120 V divided by 60 ohms equals 2 A.
Question 4: What does GFCI stand for in electrical safety?
- Ground Fault Circuit Interrupter (Correct answer)
- General Fault Current Indicator
- Grounded Fixture Circuit Isolator
- Ground Frequency Current Inspector
Correct answer: Ground Fault Circuit Interrupter
A Ground Fault Circuit Interrupter detects imbalances in current flow and quickly shuts off power to prevent electrocution.
Question 5: What is the purpose of a disconnect switch in an electrical panel?
- To safely de-energize a circuit for maintenance (Correct answer)
- To boost voltage to connected equipment
- To convert AC to DC power
- To measure power factor
Correct answer: To safely de-energize a circuit for maintenance
A disconnect switch allows a technician to safely isolate and de-energize a circuit before performing maintenance.
Question 6: Which wire color in standard US wiring indicates the neutral conductor?
- White (Correct answer)
- Black
- Green
- Red
Correct answer: White
In US standard wiring, white identifies the neutral conductor, while black or red are hot and green is ground.
What is the standard US residential single-phase voltage supplied to most homes?