Questions and Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. A 120/240V single-phase system is most commonly derived from
which transformer configuration?
A) Delta-delta
B) Wye-wye
C) Single-phase center-tapped transformer
D) Open delta
Answer: C) Single-phase center-tapped transformer
Rationale: A 120/240V single-phase system is typically produced using
a center-tapped secondary winding, which provides two 120V legs and
240V across the full winding.
2. According to general electrical practice, the primary purpose of a
grounding electrode system is to:
A) Carry normal load current
, B) Stabilize voltage to earth and provide a reference point
C) Increase circuit resistance
D) Replace overcurrent protection
Answer: B) Stabilize voltage to earth and provide a reference point
Rationale: The grounding electrode system establishes a reference to
earth and helps stabilize system voltage during normal and fault
conditions.
3. What is the maximum voltage drop recommended for branch
circuits combined with feeders under typical design guidelines?
A) 10%
B) 7%
C) 5%
D) 3%
Answer: C) 5%
Rationale: Recommended practice suggests limiting total voltage drop
to 5% for efficiency and equipment performance, typically 3% for
branch circuits and 2% for feeders.
, 4. Which device is designed to protect against overloads and short
circuits?
A) Disconnect switch
B) Grounding electrode
C) Circuit breaker
D) Transformer
Answer: C) Circuit breaker
Rationale: A circuit breaker automatically interrupts current flow
when an overload or short circuit occurs, protecting conductors and
equipment.
5. The ampacity of a conductor is primarily determined by its:
A) Color
B) Length only
C) Insulation rating and conductor size
D) Voltage rating
Answer: C) Insulation rating and conductor size
Rationale: Ampacity depends on conductor material, size
(AWG/kcmil), insulation temperature rating, and installation
conditions.
, 6. A 3-phase, 4-wire system typically includes:
A) Three hot conductors only
B) Three hot conductors and a neutral
C) Two hot conductors and a ground
D) One hot conductor and three neutrals
Answer: B) Three hot conductors and a neutral
Rationale: A 3-phase, 4-wire system includes three phase conductors
and a neutral for line-to-neutral loads.
7. The main purpose of a GFCI is to protect against:
A) Overvoltage
B) Short circuits
C) Ground faults
D) Lightning strikes
Answer: C) Ground faults
Rationale: A Ground Fault Circuit Interrupter detects leakage current
to ground and quickly disconnects power to prevent shock.
8. Which material is most commonly used for electrical conductors in
residential wiring?