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CSLB C-10 Electrical Contractor practice questions

210 free questions with answers and explanations.

Practice test
  1. 101.A 240V single-phase motor draws 30 amps with a power factor of 0.8. What is the approximate real power consumed by the motor?Electrical Theory and Calculations
  2. 102.A circuit has three resistors connected in series: R1 = 10 ohms, R2 = 20 ohms, and R3 = 30 ohms. If the total voltage supplied to the circuit is 120 volts, what is the total current flowing through the circuit?Electrical Theory and Calculations
  3. 103.A 208V, 3-phase pure resistive load draws 30 amps. What is the approximate total real power consumed by the load?Electrical Theory and Calculations
  4. 104.A three-phase motor operates on a 208V supply and draws 25 amps. If the motor has a power factor of 0.85, what is the approximate real power consumed by the motor?Electrical Theory and Calculations
  5. 105.A series circuit contains three resistors: R1 = 20 ohms, R2 = 30 ohms, and R3 = 50 ohms. If the circuit is connected to a 120V DC source, what is the total resistance of the circuit?Electrical Theory and Calculations
  6. 106.A 120V circuit powers a resistive heating element with a resistance of 10 ohms. What is the approximate current drawn by the heating element?Electrical Theory and Calculations
  7. 107.An electrician is troubleshooting a control circuit that has a 24V supply. If a relay coil in the circuit draws 50 mA of current, what is the resistance of the relay coil?Electrical Theory and Calculations
  8. 108.A conduit run needs to accommodate 4 AWG THHN conductors. According to NEC Table C.1 or relevant conduit fill calculations, what is the maximum number of 4 AWG THHN conductors permitted in a 1-1/2 inch EMT conduit?Electrical Theory and Calculations
  9. 109.A 208V, 3-phase pure resistive load draws 40 amps. What is the approximate total real power consumed by the load?Electrical Theory and Calculations
  10. 110.A technician observes that a single-phase motor operating on a 240V supply draws 15 amps with a power factor of 0.8. What is the approximate real power consumed by the motor?Electrical Theory and Calculations
  11. 111.An electrician needs to determine the maximum number of 12 AWG THHN conductors that can be installed in a 1-inch EMT conduit, assuming the conductors are all current-carrying and the conduit is less than 24 inches long (no derating for length).Electrical Theory and Calculations
  12. 112.A pilot light in a control panel consumes 15 watts of power when connected to a 24V DC supply. What is the approximate resistance of the pilot light filament?Electrical Theory and Calculations
  13. 113.A load requires 50 amps at 240V, single-phase. If the circuit conductors are 2 AWG copper, and the total one-way length of the circuit is 150 feet, what is the approximate voltage drop, assuming a specific resistance of 0.162 ohms per 1000 feet for 2 AWG copper?Electrical Theory and Calculations
  14. 114.A transformer is used to step down voltage from 2400V to 120V. If the primary current is 5 amps, what is the approximate secondary current, assuming an ideal transformer?Electrical Theory and Calculations
  15. 115.A 480V, 3-phase, 60 Hz transformer is connected Delta on the primary side and Wye on the secondary side. If the line-to-line voltage on the secondary side is 208V, what is the approximate line-to-neutral voltage on the secondary side?Electrical Theory and Calculations
  16. 116.A conduit run includes four 90-degree bends between pull points. According to the NEC, what is the maximum number of additional 90-degree bends permitted in this run before a new pull point is required?Electrical Theory and Calculations
  17. 117.A transformer has a primary winding with 200 turns and a secondary winding with 50 turns. If the primary voltage is 480V, what is the secondary voltage?Electrical Theory and Calculations
  18. 118.A 480V, 3-phase, 60 Hz transformer is connected Delta on the primary side and Wye on the secondary side. If the primary line current is 10 amps, what is the approximate phase current in the primary windings?Electrical Theory and Calculations
  19. 119.An electrician is troubleshooting a circuit and measures a voltage of 240V across a component and a current of 5A flowing through it. What is the resistance of the component?Electrical Theory and Calculations
  20. 120.A parallel circuit contains three resistors: R1 = 100 ohms, R2 = 200 ohms, and R3 = 400 ohms. What is the total equivalent resistance of this circuit?Electrical Theory and Calculations
  21. 121.A client has a 120V circuit supplying a load that draws 10 amps. If the total resistance of the conductors in the circuit is 0.5 ohms, what is the voltage drop across the conductors?Electrical Theory and Calculations
  22. 122.A 480V, 3-phase motor has a full-load current of 65 amps. If the motor's power factor is 0.85 and its efficiency is 90%, what is the approximate apparent power drawn by the motor?Electrical Theory and Calculations
  23. 123.A 2400V primary transformer drawing 5 amps is used to step down voltage to 120V on the secondary. What is the approximate current in the secondary winding, assuming an ideal transformer?Electrical Theory and Calculations
  24. 124.A 240V single-phase circuit supplies a load with 20 amps. What is the maximum voltage drop allowed for a branch circuit that is 100 feet long, if the NEC limits voltage drop to 3% for branch circuits?Electrical Theory and Calculations
  25. 125.A transformer has a primary voltage of 480V and a secondary voltage of 240V. If the primary coil has 200 turns, how many turns should the secondary coil have for ideal operation?Electrical Theory and Calculations
  26. 126.A 120-volt circuit powers a resistive heater with a current draw of 12.5 amperes. What is the power consumed by the heater?Electrical Theory and Calculations
  27. 127.A transformer has a primary winding with 600 turns and a secondary winding with 150 turns. If the primary voltage is 480V, what is the approximate secondary voltage?Electrical Theory and Calculations
  28. 128.A parallel circuit has three resistors: R1 = 10 ohms, R2 = 15 ohms, and R3 = 30 ohms. What is the total resistance of this parallel circuit?Electrical Theory and Calculations
  29. 129.An electrician is troubleshooting a circuit with a measured voltage of 24V and a current of 0.5A. What is the total resistance of this circuit?Electrical Theory and Calculations
  30. 130.A 480V, 3-phase, 60 Hz transformer is connected Delta on the primary side and Wye on the secondary side. If the secondary line-to-line voltage is 208V, what is the approximate phase voltage on the secondary side?Electrical Theory and Calculations
  31. 131.A transformer is used to step down voltage from 4800V to 240V. If the secondary current is 50 amps, what is the approximate primary current, assuming an ideal transformer?Electrical Theory and Calculations
  32. 132.A client is planning to install a new induction motor that will operate at 208V, three-phase, drawing 45 amps with a power factor of 0.8 lagging. What is the approximate apparent power for this motor?Electrical Theory and Calculations
  33. 133.A client requests a 120V circuit to power a new load drawing 1500 watts. If the circuit conductors have a total resistance of 0.2 ohms, what is the approximate voltage drop across the conductors?Electrical Theory and Calculations
  34. 134.A three-phase motor operates on a 480V supply and draws 30 amps. If the motor has a power factor of 0.85, what is the approximate reactive power consumed by the motor?Electrical Theory and Calculations
  35. 135.An electrical contractor is performing an arc flash risk assessment for a 480V motor control center. According to NFPA 70E, what is the primary factor that determines the severity of an arc flash incident and dictates the required Personal Protective Equipment (PPE)?Safety and Testing
  36. 136.During an electrical installation in a commercial building, a qualified electrician needs to verify that the newly installed grounding electrode system has sufficiently low resistance to earth. Which test method is most commonly used and required by industry standards for this purpose?Safety and Testing
  37. 137.An electrical worker is conducting a continuity test on a newly pulled feeder conductor using a multimeter. The multimeter indicates an 'OL' (Over Limit/Open Loop) reading. What does this reading most likely indicate?Safety and Testing
  38. 138.A qualified electrical worker is using a digital multimeter (DMM) to measure AC voltage on a live circuit. Before making any measurement, what is the MOST critical safety check the worker must perform on the DMM itself?Safety and Testing
  39. 139.Which type of meter is essential for testing the integrity of insulation on high-voltage cables or motor windings?Safety and Testing
  40. 140.A technician is installing a new 480V, 3-phase motor. During the pre-energization checks, they need to confirm the correct phase rotation to prevent damage to the motor. Which instrument is designed for this specific purpose?Safety and Testing
  41. 141.A qualified electrical worker is preparing to test the continuity of a de-energized 120V circuit. Which setting should be selected on a digital multimeter (DMM) for this task?Safety and Testing
  42. 142.An electrical contractor is performing work on an energized 480V panelboard, requiring an Arc Flash Hazard Analysis. The analysis indicates an incident energy level that necessitates Arc Flash PPE Category 4. Which of the following is a mandatory component of Arc Flash PPE Category 4, according to NFPA 70E?Safety and Testing
  43. 143.An electrician is checking for proper grounding of a newly installed 120V receptacle. Using a multimeter, what voltage reading should be observed between the hot (small slot) and the equipment grounding conductor (round hole) of a properly wired and grounded receptacle?Safety and Testing
  44. 144.An electrician is troubleshooting a control circuit and needs to measure current. Which of the following instruments would be most appropriate for measuring current without breaking the circuit?Safety and Testing
  45. 145.A qualified electrical worker is performing maintenance on a 480V motor control center. After de-energizing the equipment and verifying absence of voltage, the worker needs to apply personal protective grounds. According to best safety practices and NFPA 70E, what is the primary purpose of applying personal protective grounds?Safety and Testing
  46. 146.A technician is preparing to work on a 480V motor control center. Which of the following is the LAST step to verify the absence of voltage AFTER applying lockout/tagout devices?Safety and Testing
  47. 147.An electrician is troubleshooting a motor circuit and needs to measure the resistance of the motor windings. Which of the following instruments is most appropriate for this task?Safety and Testing
  48. 148.A qualified electrical worker is performing maintenance on a motor control center that has been de-energized and locked out. Before beginning work, the worker tests the circuit with a voltage detector. The detector shows no voltage, but the worker notices the detector's battery indicator is low. What is the immediate next action the worker should take according to safety protocols?Safety and Testing
  49. 149.A qualified electrical worker is performing a ground resistance test on a newly installed grounding electrode system at a commercial building. Using the fall-of-potential method with a three-point test instrument, which of the following is crucial for obtaining an accurate resistance reading?Safety and Testing
  50. 150.A qualified electrical worker is installing a new 277V lighting circuit. To comply with Cal/OSHA regulations for electrical installations, which of the following is a fundamental requirement regarding guarding of live parts?Safety and Testing