OCILB – Electrical Contractor Examination
(Commercial Electrical License) Questions and
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. Under the National Electrical Code (NEC), what is the primary
purpose of an overcurrent protective device?
A. To increase circuit voltage
B. To improve power factor
C. To protect conductors and equipment from excessive current
D. To provide a means of grounding
Answer: C. To protect conductors and equipment from excessive
current
Rationale: Overcurrent protective devices such as fuses and circuit
breakers are designed to open a circuit when current exceeds the
permitted value. This protection helps prevent conductor overheating,
equipment damage, and fire hazards.
, 2. Which conductor is normally identified by a continuous white or
gray insulation color?
A. Ungrounded conductor
B. Grounded conductor
C. Equipment grounding conductor
D. Isolated grounding conductor
Answer: B. Grounded conductor
Rationale: The grounded circuit conductor is commonly identified by
white or gray insulation. This conductor is frequently called the
neutral in many systems, although the NEC uses the more precise term
“grounded conductor.”
3. What is the minimum copper conductor size generally permitted
for a 20-ampere branch circuit under the NEC?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Answer: B. 12 AWG
Rationale: A standard 20-ampere branch circuit is generally supplied
with 12 AWG copper conductors. There are specific conditions and
,exceptions elsewhere in the NEC, but 12 AWG copper is the standard
minimum conductor size for this application.
4. What is the main function of an equipment grounding conductor?
A. Carry normal circuit current
B. Reduce operating voltage
C. Provide a low-impedance path for fault current
D. Increase circuit capacity
Answer: C. Provide a low-impedance path for fault current
Rationale: The equipment grounding conductor connects normally
non-current-carrying metal parts to the grounding system. During a
fault, it provides a path that allows sufficient current to flow so the
overcurrent protective device can operate.
5. A circuit has a 120-volt supply and a load of 12 ohms. What
current flows through the load?
A. 5 amperes
B. 10 amperes
C. 12 amperes
D. 20 amperes
Answer: B. 10 amperes
, Rationale: Ohm’s law states that current equals voltage divided by
resistance. Therefore, I = E/R = 120/12 = 10 amperes.
6. What is the purpose of a service disconnecting means?
A. To increase service voltage
B. To disconnect the premises wiring from the utility transformer
C. To disconnect the building's electrical supply from the service
conductors
D. To regulate transformer frequency
Answer: C. To disconnect the building's electrical supply from the
service conductors
Rationale: The service disconnect provides a means to disconnect the
building's electrical installation from the service supply. It is important
for maintenance, emergency response, and safe isolation of the
electrical system.
7. Which wiring method provides a raceway consisting of a flexible
metallic tubing that is commonly used where flexibility is
required?
A. EMT
B. RMC
(Commercial Electrical License) Questions and
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. Under the National Electrical Code (NEC), what is the primary
purpose of an overcurrent protective device?
A. To increase circuit voltage
B. To improve power factor
C. To protect conductors and equipment from excessive current
D. To provide a means of grounding
Answer: C. To protect conductors and equipment from excessive
current
Rationale: Overcurrent protective devices such as fuses and circuit
breakers are designed to open a circuit when current exceeds the
permitted value. This protection helps prevent conductor overheating,
equipment damage, and fire hazards.
, 2. Which conductor is normally identified by a continuous white or
gray insulation color?
A. Ungrounded conductor
B. Grounded conductor
C. Equipment grounding conductor
D. Isolated grounding conductor
Answer: B. Grounded conductor
Rationale: The grounded circuit conductor is commonly identified by
white or gray insulation. This conductor is frequently called the
neutral in many systems, although the NEC uses the more precise term
“grounded conductor.”
3. What is the minimum copper conductor size generally permitted
for a 20-ampere branch circuit under the NEC?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Answer: B. 12 AWG
Rationale: A standard 20-ampere branch circuit is generally supplied
with 12 AWG copper conductors. There are specific conditions and
,exceptions elsewhere in the NEC, but 12 AWG copper is the standard
minimum conductor size for this application.
4. What is the main function of an equipment grounding conductor?
A. Carry normal circuit current
B. Reduce operating voltage
C. Provide a low-impedance path for fault current
D. Increase circuit capacity
Answer: C. Provide a low-impedance path for fault current
Rationale: The equipment grounding conductor connects normally
non-current-carrying metal parts to the grounding system. During a
fault, it provides a path that allows sufficient current to flow so the
overcurrent protective device can operate.
5. A circuit has a 120-volt supply and a load of 12 ohms. What
current flows through the load?
A. 5 amperes
B. 10 amperes
C. 12 amperes
D. 20 amperes
Answer: B. 10 amperes
, Rationale: Ohm’s law states that current equals voltage divided by
resistance. Therefore, I = E/R = 120/12 = 10 amperes.
6. What is the purpose of a service disconnecting means?
A. To increase service voltage
B. To disconnect the premises wiring from the utility transformer
C. To disconnect the building's electrical supply from the service
conductors
D. To regulate transformer frequency
Answer: C. To disconnect the building's electrical supply from the
service conductors
Rationale: The service disconnect provides a means to disconnect the
building's electrical installation from the service supply. It is important
for maintenance, emergency response, and safe isolation of the
electrical system.
7. Which wiring method provides a raceway consisting of a flexible
metallic tubing that is commonly used where flexibility is
required?
A. EMT
B. RMC
