Questions and Correct Answers
(Verified Answers) Plus Rationales 2026
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1. Which of the following is the maximum allowable voltage drop for
a branch circuit in a commercial building?
A) 2%
B) 3%
C) 5%
D) 10%
B) 3%
Rationale: The National Electrical Code (NEC) and NYC Electrical Code
recommend that voltage drop for branch circuits should not exceed 3%
to ensure efficient operation of electrical equipment and minimize
energy losses.
, 2. What is the primary purpose of a grounding electrode system?
A) To prevent overcurrent
B) To provide a path for lightning
C) To stabilize voltage to earth
D) To increase circuit capacity
C) To stabilize voltage to earth
Rationale: Grounding electrode systems provide a reference point to
earth, stabilizing voltage levels and enhancing safety by directing fault
currents away from people and equipment.
3. Which conductor color is typically used for equipment grounding
in NYC electrical installations?
A) Black
B) White
C) Green
D) Red
C) Green
Rationale: According to the NEC and NYC Electrical Code, green (or
green with yellow stripe) is designated for equipment grounding
conductors to identify them clearly from other circuits.
, 4. The minimum working space in front of electrical equipment
operating at 600 volts is:
A) 3 feet
B) 4 feet
C) 6 feet
D) 10 feet
B) 4 feet
Rationale: NEC Article 110 requires a minimum working space of 3 to 4
feet in front of electrical equipment depending on voltage and
conditions. For equipment up to 600 volts, 4 feet is standard to allow
safe operation and maintenance.
5. Which device is designed to protect personnel from electrical
shock?
A) Circuit breaker
B) Fuse
C) Ground-fault circuit interrupter (GFCI)
D) Contactor
C) Ground-fault circuit interrupter (GFCI)
Rationale: GFCIs detect leakage currents to ground and interrupt the
circuit in milliseconds, significantly reducing the risk of electrocution.
, 6. What is the minimum size copper conductor required for a 20-
ampere branch circuit?
A) 14 AWG
B) 12 AWG
C) 10 AWG
D) 8 AWG
B) 12 AWG
Rationale: NEC Table 310.16 specifies that a 12 AWG copper conductor
is suitable for a 20-ampere circuit under normal ambient conditions.
7. Which of the following describes a 3-phase, 4-wire system?
A) Single-phase with neutral
B) Three-phase with no neutral
C) Three-phase with a neutral for line-to-neutral loads
D) Direct current system
C) Three-phase with a neutral for line-to-neutral loads
Rationale: A 3-phase, 4-wire system provides three hot conductors
plus a neutral, allowing both line-to-line and line-to-neutral loads.