Ohio Electrical Contractor Exam Practice
Questions and Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
1. What is the primary purpose of an equipment grounding conductor?
A. To carry normal circuit current
B. To increase circuit voltage
C. To provide a path for fault current
D. To reduce the load on a transformer
Correct Answer: C. To provide a path for fault current
Rationale: The equipment grounding conductor provides an effective path for fault
current back to the source so that the overcurrent protective device can operate
and clear the fault.
2. Which unit is used to measure electrical resistance?
A. Watt
B. Ohm
C. Ampere
D. Volt
Correct Answer: B. Ohm
Rationale: The ohm (Ω) is the standard unit of electrical resistance. Ohm's law
relates resistance, voltage, and current as R = V ÷ I.
3. A 120-volt load draws 15 amperes. What is the load's power consumption?
A. 1,800 watts
B. 135 watts
,C. 8 watts
D. 1,200 watts
Correct Answer: A. 1,800 watts
Rationale: Electrical power can be calculated using P = V × I. Therefore, 120 volts ×
15 amperes = 1,800 watts.
4. What is the primary function of a transformer?
A. To provide overcurrent protection
B. To increase conductor ampacity
C. To interrupt a fault
D. To change the voltage level of an AC circuit
Correct Answer: D. To change the voltage level of an AC circuit
Rationale: A transformer transfers electrical energy between windings through
electromagnetic induction and can step voltage up or down.
5. A transformer has a 480-volt primary and a 120-volt secondary. What type of
transformation occurs?
A. Step-down
B. Step-up
C. Isolation with increased voltage
D. Frequency conversion
Correct Answer: A. Step-down
Rationale: The secondary voltage is lower than the primary voltage, so the
transformer is stepping the voltage down from 480 volts to 120 volts.
6. What is the primary purpose of a transformer enclosure?
A. To increase transformer efficiency
B. To provide physical protection for the transformer and its components
,C. To increase the secondary voltage
D. To eliminate the need for grounding
Correct Answer: B. To provide physical protection for the transformer and its
components
Rationale: An enclosure protects electrical components from physical damage and
helps control access to energized parts.
7. A 120/240-volt single-phase service supplies a balanced load of 30 amperes
on each ungrounded conductor. What is the line-to-line voltage?
A. 120 volts
B. 208 volts
C. 240 volts
D. 480 volts
Correct Answer: C. 240 volts
Rationale: A standard 120/240-volt single-phase system provides 240 volts
between the two ungrounded conductors and 120 volts between either
ungrounded conductor and the grounded conductor.
8. What is the primary purpose of a service disconnecting means?
A. To increase service capacity
B. To disconnect the premises wiring from the supply
C. To regulate transformer temperature
D. To increase conductor ampacity
Correct Answer: B. To disconnect the premises wiring from the supply
Rationale: The service disconnecting means provides a means of disconnecting the
premises from the electrical supply for safety and servicing.
, 9. A branch circuit supplies a continuous load of 16 amperes. Using the standard
125% continuous-load factor, what minimum ampacity is required for the circuit
conductors?
A. 16 A
B. 18 A
C. 20 A
D. 24 A
Correct Answer: D. 20 A
Rationale: The continuous load is multiplied by 125%: 16 A × 1.25 = 20 A. The
conductors must have adequate ampacity for the resulting load.
10. What is the primary purpose of overcurrent protection for a feeder?
A. To protect conductors from excessive current
B. To increase the feeder's voltage
C. To improve power factor
D. To eliminate voltage drop
Correct Answer: A. To protect conductors from excessive current
Rationale: Overcurrent protective devices are intended to limit current to levels
the conductors and equipment can safely withstand under applicable conditions.
11. Which factor is important when determining conductor ampacity?
A. The color of the conductor insulation
B. The number of current-carrying conductors in a raceway
C. The manufacturer's logo
D. The physical color of the raceway
Correct Answer: B. The number of current-carrying conductors in a raceway
Rationale: Multiple current-carrying conductors can increase heat buildup, which
may require ampacity adjustment according to applicable NEC requirements.
Questions and Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
1. What is the primary purpose of an equipment grounding conductor?
A. To carry normal circuit current
B. To increase circuit voltage
C. To provide a path for fault current
D. To reduce the load on a transformer
Correct Answer: C. To provide a path for fault current
Rationale: The equipment grounding conductor provides an effective path for fault
current back to the source so that the overcurrent protective device can operate
and clear the fault.
2. Which unit is used to measure electrical resistance?
A. Watt
B. Ohm
C. Ampere
D. Volt
Correct Answer: B. Ohm
Rationale: The ohm (Ω) is the standard unit of electrical resistance. Ohm's law
relates resistance, voltage, and current as R = V ÷ I.
3. A 120-volt load draws 15 amperes. What is the load's power consumption?
A. 1,800 watts
B. 135 watts
,C. 8 watts
D. 1,200 watts
Correct Answer: A. 1,800 watts
Rationale: Electrical power can be calculated using P = V × I. Therefore, 120 volts ×
15 amperes = 1,800 watts.
4. What is the primary function of a transformer?
A. To provide overcurrent protection
B. To increase conductor ampacity
C. To interrupt a fault
D. To change the voltage level of an AC circuit
Correct Answer: D. To change the voltage level of an AC circuit
Rationale: A transformer transfers electrical energy between windings through
electromagnetic induction and can step voltage up or down.
5. A transformer has a 480-volt primary and a 120-volt secondary. What type of
transformation occurs?
A. Step-down
B. Step-up
C. Isolation with increased voltage
D. Frequency conversion
Correct Answer: A. Step-down
Rationale: The secondary voltage is lower than the primary voltage, so the
transformer is stepping the voltage down from 480 volts to 120 volts.
6. What is the primary purpose of a transformer enclosure?
A. To increase transformer efficiency
B. To provide physical protection for the transformer and its components
,C. To increase the secondary voltage
D. To eliminate the need for grounding
Correct Answer: B. To provide physical protection for the transformer and its
components
Rationale: An enclosure protects electrical components from physical damage and
helps control access to energized parts.
7. A 120/240-volt single-phase service supplies a balanced load of 30 amperes
on each ungrounded conductor. What is the line-to-line voltage?
A. 120 volts
B. 208 volts
C. 240 volts
D. 480 volts
Correct Answer: C. 240 volts
Rationale: A standard 120/240-volt single-phase system provides 240 volts
between the two ungrounded conductors and 120 volts between either
ungrounded conductor and the grounded conductor.
8. What is the primary purpose of a service disconnecting means?
A. To increase service capacity
B. To disconnect the premises wiring from the supply
C. To regulate transformer temperature
D. To increase conductor ampacity
Correct Answer: B. To disconnect the premises wiring from the supply
Rationale: The service disconnecting means provides a means of disconnecting the
premises from the electrical supply for safety and servicing.
, 9. A branch circuit supplies a continuous load of 16 amperes. Using the standard
125% continuous-load factor, what minimum ampacity is required for the circuit
conductors?
A. 16 A
B. 18 A
C. 20 A
D. 24 A
Correct Answer: D. 20 A
Rationale: The continuous load is multiplied by 125%: 16 A × 1.25 = 20 A. The
conductors must have adequate ampacity for the resulting load.
10. What is the primary purpose of overcurrent protection for a feeder?
A. To protect conductors from excessive current
B. To increase the feeder's voltage
C. To improve power factor
D. To eliminate voltage drop
Correct Answer: A. To protect conductors from excessive current
Rationale: Overcurrent protective devices are intended to limit current to levels
the conductors and equipment can safely withstand under applicable conditions.
11. Which factor is important when determining conductor ampacity?
A. The color of the conductor insulation
B. The number of current-carrying conductors in a raceway
C. The manufacturer's logo
D. The physical color of the raceway
Correct Answer: B. The number of current-carrying conductors in a raceway
Rationale: Multiple current-carrying conductors can increase heat buildup, which
may require ampacity adjustment according to applicable NEC requirements.
