Chicago DOB – Electrical Contractor License
Examination Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
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1. What is the primary purpose of an electrical equipment grounding
conductor (EGC)?
A. To carry normal circuit current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce the resistance of the grounded conductor
Answer: C. To provide a low-impedance path for fault current
Rationale: The equipment grounding conductor provides a low-
impedance path back to the source when a fault places energized
metal parts at an abnormal voltage. This allows the overcurrent
protective device to operate quickly and disconnect the faulted circuit.
,2. Which NEC article primarily covers branch circuits?
A. Article 100
B. Article 210
C. Article 250
D. Article 300
Answer: B. Article 210
Rationale: NEC Article 210 contains requirements for branch circuits,
including their ratings, required outlets, overcurrent protection,
receptacle requirements, and conductor provisions. Article 250 focuses
on grounding and bonding, while Article 300 addresses general wiring
methods.
3. A 120-volt branch circuit supplies a continuous load of 16 amperes.
Using the standard 125% continuous-load rule, what minimum
ampacity is required?
A. 16 A
B. 18 A
C. 20 A
D. 25 A
Answer: C. 20 A
,Rationale: A continuous load is generally calculated at 125% for
conductor and overcurrent protection purposes. The calculation is 16
A × 1.25 = 20 A, so a conductor with an allowable ampacity of at least
20 amperes is required, subject to applicable NEC adjustments and
limitations.
4. What is the main function of a circuit breaker?
A. To increase voltage
B. To protect against excessive current
C. To provide grounding electrode resistance
D. To improve power factor
Answer: B. To protect against excessive current
Rationale: A circuit breaker is an overcurrent protective device. It
opens the circuit when current exceeds its rating under conditions
covered by its trip characteristics, helping protect conductors and
equipment from excessive current.
5. Which conductor normally carries current back to the source on a
typical single-phase 120-volt circuit?
, A. Equipment grounding conductor
B. Grounding electrode conductor
C. Grounded conductor
D. Bonding jumper
Answer: C. Grounded conductor
Rationale: In a typical 120-volt circuit, the grounded conductor,
commonly called the neutral, provides the return path for unbalanced
or load current. The equipment grounding conductor is not intended
to carry normal operating current.
6. What is the purpose of bonding normally non-current-carrying
metal parts together?
A. To increase operating voltage
B. To create an effective fault-current path
C. To eliminate all voltage drop
D. To replace overcurrent protection
Answer: B. To create an effective fault-current path
Rationale: Bonding connects conductive parts together so that, during
a fault, current can travel along an effective path back to the source.
Examination Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of an electrical equipment grounding
conductor (EGC)?
A. To carry normal circuit current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce the resistance of the grounded conductor
Answer: C. To provide a low-impedance path for fault current
Rationale: The equipment grounding conductor provides a low-
impedance path back to the source when a fault places energized
metal parts at an abnormal voltage. This allows the overcurrent
protective device to operate quickly and disconnect the faulted circuit.
,2. Which NEC article primarily covers branch circuits?
A. Article 100
B. Article 210
C. Article 250
D. Article 300
Answer: B. Article 210
Rationale: NEC Article 210 contains requirements for branch circuits,
including their ratings, required outlets, overcurrent protection,
receptacle requirements, and conductor provisions. Article 250 focuses
on grounding and bonding, while Article 300 addresses general wiring
methods.
3. A 120-volt branch circuit supplies a continuous load of 16 amperes.
Using the standard 125% continuous-load rule, what minimum
ampacity is required?
A. 16 A
B. 18 A
C. 20 A
D. 25 A
Answer: C. 20 A
,Rationale: A continuous load is generally calculated at 125% for
conductor and overcurrent protection purposes. The calculation is 16
A × 1.25 = 20 A, so a conductor with an allowable ampacity of at least
20 amperes is required, subject to applicable NEC adjustments and
limitations.
4. What is the main function of a circuit breaker?
A. To increase voltage
B. To protect against excessive current
C. To provide grounding electrode resistance
D. To improve power factor
Answer: B. To protect against excessive current
Rationale: A circuit breaker is an overcurrent protective device. It
opens the circuit when current exceeds its rating under conditions
covered by its trip characteristics, helping protect conductors and
equipment from excessive current.
5. Which conductor normally carries current back to the source on a
typical single-phase 120-volt circuit?
, A. Equipment grounding conductor
B. Grounding electrode conductor
C. Grounded conductor
D. Bonding jumper
Answer: C. Grounded conductor
Rationale: In a typical 120-volt circuit, the grounded conductor,
commonly called the neutral, provides the return path for unbalanced
or load current. The equipment grounding conductor is not intended
to carry normal operating current.
6. What is the purpose of bonding normally non-current-carrying
metal parts together?
A. To increase operating voltage
B. To create an effective fault-current path
C. To eliminate all voltage drop
D. To replace overcurrent protection
Answer: B. To create an effective fault-current path
Rationale: Bonding connects conductive parts together so that, during
a fault, current can travel along an effective path back to the source.
