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CSLB C-10 Electrical Contractor practice questions

210 free questions with answers and explanations.

Practice test
  1. 151.An electrical contractor is preparing to perform maintenance on a 277V lighting circuit. To ensure safety, a qualified person must conduct an arc flash risk assessment. What is the primary outcome of this assessment according to NFPA 70E?Safety and Testing
  2. 152.According to NFPA 70E, what is the primary purpose of an Arc Flash Boundary (AFB)?Safety and Testing
  3. 153.A contractor is installing new electrical equipment in a commercial building. According to Cal/OSHA, which of the following is a primary requirement for grounding and bonding of this equipment?Safety and Testing
  4. 154.A technician is performing an insulation resistance test on a newly installed 480V motor feeder circuit using a megohmmeter (Megger). The test results show an insulation resistance of 2 megohms. According to industry best practices and common standards, what does this reading indicate for a 480V system?Safety and Testing
  5. 155.A qualified electrical worker needs to verify the proper operation of a ground-fault circuit interrupter (GFCI) receptacle after installation. Which of the following is the correct method to test a GFCI receptacle?Safety and Testing
  6. 156.According to Cal/OSHA, if an electrical hazard is identified that cannot be eliminated or reduced to a safe level, what is the LAST resort for protecting workers?Safety and Testing
  7. 157.A technician observes an unlabeled piece of electrical equipment in an industrial facility. According to Cal/OSHA, what is the primary purpose of proper labeling and identification for electrical equipment?Safety and Testing
  8. 158.During an arc flash risk assessment, an electrical contractor determines that the incident energy at a specific piece of equipment is 9 cal/cm². According to NFPA 70E, what is the minimum Arc Flash PPE Category (Hazard/Risk Category) required for work on this equipment, assuming the hazard cannot be eliminated?Safety and Testing
  9. 159.A qualified electrical worker is decommissioning a 600V motor control center. After de-energizing the equipment and applying lockout/tagout devices, what is the next critical step before beginning work, according to NFPA 70E?Safety and Testing
  10. 160.A qualified worker is using a digital multimeter (DMM) to measure AC voltage on a live circuit. Before making any measurements, what essential safety step must be performed related to the DMM itself?Safety and Testing
  11. 161.A qualified electrical worker is performing a routine inspection of an industrial panelboard. They notice that a piece of equipment connected to the panel is not properly grounded, posing a shock hazard. According to Cal/OSHA, what is the most effective control measure to implement FIRST to address this hazard?Safety and Testing
  12. 162.A qualified electrical worker is preparing to perform maintenance on a 480V motor control center. Before commencing work, they must de-energize the equipment and apply appropriate lockout/tagout devices. According to NFPA 70E, which of the following is the LAST step a qualified person must perform to verify an electrically safe work condition?Safety and Testing
  13. 163.A commercial building has a 400-ampere, 208Y/120-volt service. The design calls for a main service disconnect and two sub-panels, each with its own main breaker. The service conductors are run in EMT conduit. How many readily accessible service disconnects are permitted at this location?Equipment and Installation
  14. 164.An electrician is installing two 3-phase, 480-volt feeders in the same conduit. Each feeder consists of three 4 AWG THHN copper conductors. What is the maximum number of current-carrying conductors for the purpose of adjusting ampacity according to NEC Table 310.15(C)(1)?Equipment and Installation
  15. 165.A client requests a new dedicated 20-ampere, 120-volt branch circuit for a single-phase, continuous-duty motor. The motor has a nameplate full-load current (FLC) of 15 amperes. What is the minimum size copper THWN-2 conductor required for this branch circuit?Equipment and Installation
  16. 166.A commercial kitchen is undergoing renovation. A new 120-volt, 20-ampere receptacle is being installed on a countertop. According to the California Electrical Code (CEC), what is the maximum distance this receptacle can be from the edge of the sink without requiring ground-fault circuit interrupter (GFCI) protection?Equipment and Installation
  17. 167.An electrician is installing a 200-ampere, 120/240-volt single-phase panelboard in a retail store. The panelboard will serve general lighting and receptacle loads. What is the minimum required working space depth in front of this panelboard if the panelboard is opposite a grounded masonry wall?Equipment and Installation
  18. 168.A technician is testing an AC circuit with a total impedance of 15 ohms and a power factor of 0.8 lagging. If the circuit is supplied by a 120V source, what is the approximate resistance of the circuit?Electrical Theory and Calculations
  19. 169.A technician is troubleshooting a 120V AC circuit that includes a capacitor. If the capacitor has a capacitance of 50 µF and the circuit operates at 60 Hz, what is the approximate capacitive reactance (Xc) of the capacitor?Electrical Theory and Calculations
  20. 170.A client is planning an installation where a 480V, 3-phase feeder will supply a step-down transformer to provide 208Y/120V power. If the primary winding has 1200 turns, how many turns are required on the secondary winding for the 208V line-to-line output?Electrical Theory and Calculations
  21. 171.A qualified electrical worker is performing a ground resistance test using the Fall-of-Potential method. The current electrode (P2) is placed 100 feet from the ground electrode under test, and the potential electrode (P1) is placed at 62 feet. If the meter reads 15 ohms, what is the ground resistance?Safety and Testing
  22. 172.An electrician is using a digital multimeter (DMM) to troubleshoot a 120V control circuit. The DMM display shows 'OL' when attempting to measure resistance across a de-energized coil. What does this reading most likely indicate?Safety and Testing
  23. 173.A client is installing a new 240V, 3-phase motor with a full-load current of 50 amps. If the motor has a power factor of 0.85, what is its approximate real power consumption?Electrical Theory and Calculations
  24. 174.An electrician is installing a 240V, single-phase circuit to power a new resistive oven drawing 30 amps. What is the total impedance of the circuit?Electrical Theory and Calculations
  25. 175.A qualified electrical worker is using a DMM to measure AC voltage on a live 277V circuit. Before making contact with the circuit, which of the following is the MOST critical safety check to perform on the DMM?Safety and Testing
  26. 176.A client has an existing 240V single-phase motor that draws 20 amps with a power factor of 0.75. What is the approximate reactive power consumed by this motor?Electrical Theory and Calculations
  27. 177.A qualified electrical worker is preparing to perform maintenance on a 480V motor control center. After de-energizing the equipment and verifying absence of voltage, what is the NEXT critical step according to NFPA 70E before beginning work?Safety and Testing
  28. 178.A qualified electrical worker is performing maintenance on a de-energized 480V motor control center. After de-energizing the equipment and verifying the absence of voltage, the worker needs to prevent accidental re-energization during the work. Which of the following is the most effective and compliant method to achieve this according to Cal/OSHA?Safety and Testing
  29. 179.A client needs to install a new circuit for a motor that draws a continuous current of 25 amps. According to the NEC, what is the minimum standard overcurrent protective device (OCPD) rating required for this circuit, assuming the conductor ampacity is correctly sized?Electrical Theory and Calculations
  30. 180.A commercial building has a 400-ampere, 208Y/120-volt service. The design calls for a main service disconnect and two additional individual disconnects for specific loads, each rated at 100 amperes. All disconnects are grouped in a single enclosure. Which of the following statements is true regarding the number of service disconnects allowed by the NEC?Equipment and Installation
  31. 181.A three-phase, 480V feeder circuit supplies a 75 kVA continuous load located 150 feet from the panel. The conductors are copper THHN, and the voltage drop must not exceed 3%. What is the minimum required conductor size?Wiring Methods and Materials
  32. 182.A client is planning a new commercial office building. The blueprints specify a 208V, 3-phase, 4-wire feeder for general power and lighting. The total connected load for this feeder is calculated to be 75 kVA. What is the minimum required feeder ampacity?Planning and Estimating
  33. 183.A new industrial motor control center requires a feeder connection. The feeder conductors will be 750 kcmil THHN aluminum. The terminals on the circuit breaker and the motor control center are both rated for 75°C. What is the maximum allowable ampacity for each 750 kcmil THHN aluminum conductor under these conditions, assuming no more than three current-carrying conductors in the raceway?Wiring Methods and Materials
  34. 184.An electrical contractor is preparing a material takeoff for a new residential dwelling. The blueprints indicate a symbol consisting of a circle with a single vertical line extending upward from its top, and a single horizontal line passing through the center of the circle, with a short diagonal line on the left side of the horizontal line. What does this symbol represent?Planning and Estimating
  35. 185.An electrician is installing a new solar array on a rooftop. The DC wiring from the PV modules to the inverter will be run in conduit exposed to direct sunlight and varying weather conditions. Which type of conduit is generally NOT suitable for outdoor use in this application without additional protection or specific listing?Wiring Methods and Materials
  36. 186.An electrician is installing a new solar array on a rooftop. The DC wiring from the PV modules will run in conduit across the roof. The local Authority Having Jurisdiction (AHJ) requires that all conduit be suitable for direct sunlight exposure and extreme temperature variations. Which of the following conduit types is generally NOT suitable for direct outdoor exposure to sunlight and temperature extremes without special considerations or coatings?Wiring Methods and Materials
  37. 187.A pilot light for an industrial control panel must be installed in a hazardous location where ignitable fibers are present. The wiring method must be suitable for such an environment. Which of the following wiring methods is generally NOT permitted in a Class III, Division 1 hazardous location?Wiring Methods and Materials
  38. 188.A client is planning to install a new central air conditioning unit requiring a 240V, 40A dedicated circuit. The unit will be located 100 feet from the panel. The maximum allowable voltage drop is 3%. According to NEC recommendations, what is the minimum AWG copper conductor size required for this branch circuit?Planning and Estimating
  39. 189.A technician is installing a new 120-volt, 20-ampere receptacle in a commercial kitchen, 3 feet from the edge of a permanently installed sink. Which of the following best describes the GFCI protection requirement for this receptacle according to the California Electrical Code?Equipment and Installation
  40. 190.A material takeoff for a new commercial office space includes several lighting branch circuits. Each circuit is 120V and serves 10 LED luminaires, with each luminaire rated at 100 VA. The luminaires are expected to operate continuously for more than 3 hours daily. What is the minimum continuous load current that must be used for sizing the overcurrent protective device (OCPD) for one of these branch circuits?Planning and Estimating
  41. 191.A contractor is installing a new service mast on the exterior of a commercial building. The service mast is made of 2-inch Rigid Metal Conduit (RMC). The service-entrance conductors are 4/0 AWG THWN copper. What is the maximum number of 4/0 AWG THWN copper conductors permitted in this 2-inch RMC service mast, assuming no more than 40% fill?Wiring Methods and Materials
  42. 192.A material takeoff for a new commercial office space includes several lighting branch circuits. Each circuit serves 10 fluorescent fixtures, with each fixture rated at 0.5A at 120V. If these circuits are expected to operate for more than 3 hours at a time, what is the minimum calculated load in VA for each circuit to correctly size the overcurrent protective device (OCPD)?Planning and Estimating
  43. 193.A residential client is planning a new laundry room. The plans specify a 120V, 20A branch circuit to serve a 4.5 kW electric clothes dryer. What is the minimum continuous load percentage that must be applied to the calculated dryer load when sizing the overcurrent protective device (OCPD) for this circuit?Planning and Estimating
  44. 194.A commercial client requires a new 208V, 3-phase, 40A feeder for a motor load. The feeder will run 150 feet from the panel to the motor. The conductor insulation type is THHN, and the maximum allowable voltage drop is 3%. What is the minimum AWG copper conductor size required?Planning and Estimating
  45. 195.An electrician is reviewing blueprints for a new commercial building. The general notes specify that all conductors for branch circuits are to be rated at 75°C. For a 120V, 20A general-purpose branch circuit, what is the minimum allowable ampacity of the conductors before applying any adjustment or correction factors, assuming copper conductors?Planning and Estimating
  46. 196.A client requests a new 20A, 120V branch circuit to an outdoor shed. The circuit will be protected by a GFCI circuit breaker. What is the minimum burial depth required for a Type UF cable directly buried under a driveway, if no other protection is provided?Wiring Methods and Materials
  47. 197.An electrical contractor is preparing a material takeoff for a new commercial office building. The blueprints indicate a symbol for a specific type of receptacle: a circle with two horizontal lines through it, and a 'WP' next to it. What does this symbol represent?Planning and Estimating
  48. 198.A client requests a new dedicated 20-ampere, 120-volt branch circuit for a single-phase, hermetic refrigerant motor-compressor. The motor-compressor has a nameplate rated-load current (RLC) of 15 amperes and a branch-circuit selection current (BCSC) of 18 amperes. What is the minimum continuous current rating required for the branch-circuit overcurrent protective device (OCPD)?Equipment and Installation
  49. 199.An electrician is installing a new 120V, 20A general-purpose receptacle branch circuit in a commercial office. The circuit will consist of 10 duplex receptacles. According to the NEC, what is the minimum calculated load for these receptacles for the purpose of service or feeder calculations?Planning and Estimating
  50. 200.A client is planning a new commercial office building. The blueprints specify a 208V, 3-phase, 4-wire service with a total general lighting load of 30,000 VA and 15,000 VA of receptacle loads. All loads are considered non-continuous. What is the minimum calculated demand load for the general lighting and receptacle loads, before applying any demand factors for receptacles?Planning and Estimating