CALIFORNIA ELECTRICAL CONTRACTOR
LICENSE EXAM (C-10)
Questions and Answer (Verified Answers) plus Rationales 2026 Q&A
California Electrical Contractor License Exam (C-10) Page 1
, Multiple-Choice Examination
Select the best answer for each question. This practice paper is for study purposes; verify current requirements against the California
Contractors State License Board guidance, the locally adopted electrical code, and applicable amendments.
1. Which document establishes the minimum requirements for safe electrical installations in the United
States?
A. National Fire Alarm Code only
B. National Electrical Code (NEC)
C. International Plumbing Code
D. Uniform Mechanical Code
2. What is the primary purpose of overcurrent protection?
A. To eliminate the need for grounding
B. To measure power factor
C. To protect conductors and equipment from excessive current
D. To increase circuit voltage
3. What is the main function of an equipment grounding conductor?
A. Carry normal load current continuously
B. Replace the grounded neutral conductor
C. Increase resistance to ground faults
D. Provide a low-impedance fault-current path
4. Which instrument is most appropriate for checking whether a circuit is energized?
A. A properly rated voltage tester or multimeter
B. A tape measure
C. A clamp meter used without checking its rating
D. A continuity buzzer on a live circuit
5. What should be done before servicing electrical equipment?
A. Assume the circuit is de-energized if no light is on
B. Apply an appropriate lockout/tagout procedure and verify absence of voltage
C. Rely only on the wall switch
D. Remove the equipment grounding conductor
6. Why must conductor ampacity be selected with installation conditions in mind?
A. Conduit removes all heat
B. Insulation color determines ampacity
C. Temperature, bundling, and terminal ratings can affect allowable current
D. Copper conductors always carry unlimited current
7. What is the purpose of a ground-fault circuit-interrupter (GFCI)?
A. Protect only against overloads
B. Regulate frequency
C. Replace all circuit breakers
D. Detect certain current imbalances and disconnect power quickly
8. What does an arc-fault circuit-interrupter (AFCI) primarily help detect?
A. Potentially hazardous arcing conditions
B. Low water pressure
C. Excessive pipe temperature
D. Normal changes in lighting level
California Electrical Contractor License Exam (C-10) Page 2
, 9. What is the purpose of bonding metal enclosures and raceways?
A. Serve as the normal neutral path
B. Maintain electrical continuity and a fault-current path
C. Prevent all electromagnetic fields
D. Increase circuit resistance
10. Which factor is essential when choosing a circuit breaker?
A. The length of the manufacturer's logo
B. The number of unused screws
C. Conductor protection, load characteristics, and available fault current
D. The color of the panel door
11. What does a single-line diagram communicate?
A. The exact physical route of every screw
B. Only the building's plumbing layout
C. A list of employee working hours
D. A simplified representation of an electrical power system
12. Why are panel directories important?
A. They identify the circuits served by breakers or fuses
B. They increase the panel's voltage
C. They replace required overcurrent protection
D. They prevent all short circuits
13. What is the unit of electrical resistance?
A. Volt
B. Ohm
C. Watt
D. Ampere
14. According to Ohm's law, current is calculated by which relationship?
A. I = R ÷ V
B. I = V + R
C. I = V ÷ R
D. I = V × R
15. A 120 V load draws 5 A. What is its apparent power if the load is single-phase and the stated values are
RMS?
A. 24 VA
B. 125 VA
C. 6000 VA
D. 600 VA
16. What is the approximate real power of a 240 V single-phase load drawing 10 A at a power factor of 0.8?
A. 1,920 W
B. 2,400 W
C. 300 W
D. 24,000 W
17. In a balanced three-phase system, which formula gives apparent power?
A. S = frequency × resistance
B. S = √3 × line voltage × line current
C. S = line voltage ÷ line current
D. S = 3 ÷ resistance
California Electrical Contractor License Exam (C-10) Page 3
, 18. What is the purpose of a transformer?
A. Store unlimited electrical energy
B. Guarantee zero losses
C. Transfer electrical energy between circuits through electromagnetic induction
D. Convert AC directly into plumbing pressure
19. What does a transformer turns ratio primarily determine?
A. The building's occupancy classification
B. The earth electrode resistance by itself
C. The conduit fill percentage
D. The ideal voltage ratio between primary and secondary windings
20. Why is phase sequence important on a three-phase motor?
A. It affects the direction of rotation
B. It determines conductor color in every jurisdiction
C. It eliminates the need for overload protection
D. It makes voltage irrelevant
21. When installing conductors in a raceway, what must be checked before pulling them?
A. Whether the panel directory is laminated
B. Raceway fill, conductor insulation compatibility, bend limits, and pulling conditions
C. The paint color of the raceway
D. The number of windows nearby
22. What is a key reason to protect cables where they pass through metal framing?
A. To reduce the need for supports
B. To turn the frame into a neutral conductor
C. To prevent abrasion or damage to conductor insulation
D. To increase the circuit frequency
23. What should determine the type of raceway used in a damp or corrosive location?
A. The installer's favorite brand
B. Only the wall color
C. The number of receptacles on the floor
D. The environment, listing, code requirements, and exposure
24. Why should conductors be lubricated only with a product suitable for the wire insulation?
A. Incompatible lubricants can damage insulation or affect pulling performance
B. All lubricants reduce conductor resistance to zero
C. Lubricant changes AC into DC
D. Lubricant replaces conductor sizing calculations
25. What is the role of an overload relay in a motor starter?
A. Replace the disconnecting means
B. Protect the motor against sustained overload conditions
C. Provide the branch-circuit short-circuit protection by itself in every case
D. Increase the motor's horsepower
26. Why is a motor disconnecting means required to be appropriately located and rated?
A. To eliminate grounding
B. To provide lighting control
C. To permit safe isolation for servicing and suit the motor circuit
D. To increase starting current
California Electrical Contractor License Exam (C-10) Page 4
LICENSE EXAM (C-10)
Questions and Answer (Verified Answers) plus Rationales 2026 Q&A
California Electrical Contractor License Exam (C-10) Page 1
, Multiple-Choice Examination
Select the best answer for each question. This practice paper is for study purposes; verify current requirements against the California
Contractors State License Board guidance, the locally adopted electrical code, and applicable amendments.
1. Which document establishes the minimum requirements for safe electrical installations in the United
States?
A. National Fire Alarm Code only
B. National Electrical Code (NEC)
C. International Plumbing Code
D. Uniform Mechanical Code
2. What is the primary purpose of overcurrent protection?
A. To eliminate the need for grounding
B. To measure power factor
C. To protect conductors and equipment from excessive current
D. To increase circuit voltage
3. What is the main function of an equipment grounding conductor?
A. Carry normal load current continuously
B. Replace the grounded neutral conductor
C. Increase resistance to ground faults
D. Provide a low-impedance fault-current path
4. Which instrument is most appropriate for checking whether a circuit is energized?
A. A properly rated voltage tester or multimeter
B. A tape measure
C. A clamp meter used without checking its rating
D. A continuity buzzer on a live circuit
5. What should be done before servicing electrical equipment?
A. Assume the circuit is de-energized if no light is on
B. Apply an appropriate lockout/tagout procedure and verify absence of voltage
C. Rely only on the wall switch
D. Remove the equipment grounding conductor
6. Why must conductor ampacity be selected with installation conditions in mind?
A. Conduit removes all heat
B. Insulation color determines ampacity
C. Temperature, bundling, and terminal ratings can affect allowable current
D. Copper conductors always carry unlimited current
7. What is the purpose of a ground-fault circuit-interrupter (GFCI)?
A. Protect only against overloads
B. Regulate frequency
C. Replace all circuit breakers
D. Detect certain current imbalances and disconnect power quickly
8. What does an arc-fault circuit-interrupter (AFCI) primarily help detect?
A. Potentially hazardous arcing conditions
B. Low water pressure
C. Excessive pipe temperature
D. Normal changes in lighting level
California Electrical Contractor License Exam (C-10) Page 2
, 9. What is the purpose of bonding metal enclosures and raceways?
A. Serve as the normal neutral path
B. Maintain electrical continuity and a fault-current path
C. Prevent all electromagnetic fields
D. Increase circuit resistance
10. Which factor is essential when choosing a circuit breaker?
A. The length of the manufacturer's logo
B. The number of unused screws
C. Conductor protection, load characteristics, and available fault current
D. The color of the panel door
11. What does a single-line diagram communicate?
A. The exact physical route of every screw
B. Only the building's plumbing layout
C. A list of employee working hours
D. A simplified representation of an electrical power system
12. Why are panel directories important?
A. They identify the circuits served by breakers or fuses
B. They increase the panel's voltage
C. They replace required overcurrent protection
D. They prevent all short circuits
13. What is the unit of electrical resistance?
A. Volt
B. Ohm
C. Watt
D. Ampere
14. According to Ohm's law, current is calculated by which relationship?
A. I = R ÷ V
B. I = V + R
C. I = V ÷ R
D. I = V × R
15. A 120 V load draws 5 A. What is its apparent power if the load is single-phase and the stated values are
RMS?
A. 24 VA
B. 125 VA
C. 6000 VA
D. 600 VA
16. What is the approximate real power of a 240 V single-phase load drawing 10 A at a power factor of 0.8?
A. 1,920 W
B. 2,400 W
C. 300 W
D. 24,000 W
17. In a balanced three-phase system, which formula gives apparent power?
A. S = frequency × resistance
B. S = √3 × line voltage × line current
C. S = line voltage ÷ line current
D. S = 3 ÷ resistance
California Electrical Contractor License Exam (C-10) Page 3
, 18. What is the purpose of a transformer?
A. Store unlimited electrical energy
B. Guarantee zero losses
C. Transfer electrical energy between circuits through electromagnetic induction
D. Convert AC directly into plumbing pressure
19. What does a transformer turns ratio primarily determine?
A. The building's occupancy classification
B. The earth electrode resistance by itself
C. The conduit fill percentage
D. The ideal voltage ratio between primary and secondary windings
20. Why is phase sequence important on a three-phase motor?
A. It affects the direction of rotation
B. It determines conductor color in every jurisdiction
C. It eliminates the need for overload protection
D. It makes voltage irrelevant
21. When installing conductors in a raceway, what must be checked before pulling them?
A. Whether the panel directory is laminated
B. Raceway fill, conductor insulation compatibility, bend limits, and pulling conditions
C. The paint color of the raceway
D. The number of windows nearby
22. What is a key reason to protect cables where they pass through metal framing?
A. To reduce the need for supports
B. To turn the frame into a neutral conductor
C. To prevent abrasion or damage to conductor insulation
D. To increase the circuit frequency
23. What should determine the type of raceway used in a damp or corrosive location?
A. The installer's favorite brand
B. Only the wall color
C. The number of receptacles on the floor
D. The environment, listing, code requirements, and exposure
24. Why should conductors be lubricated only with a product suitable for the wire insulation?
A. Incompatible lubricants can damage insulation or affect pulling performance
B. All lubricants reduce conductor resistance to zero
C. Lubricant changes AC into DC
D. Lubricant replaces conductor sizing calculations
25. What is the role of an overload relay in a motor starter?
A. Replace the disconnecting means
B. Protect the motor against sustained overload conditions
C. Provide the branch-circuit short-circuit protection by itself in every case
D. Increase the motor's horsepower
26. Why is a motor disconnecting means required to be appropriately located and rated?
A. To eliminate grounding
B. To provide lighting control
C. To permit safe isolation for servicing and suit the motor circuit
D. To increase starting current
California Electrical Contractor License Exam (C-10) Page 4
