CA Electrical PrepC-10 · by MITRYXA
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Free C-10 Practice Questions: Startup, Troubleshooting & Maintenance

60 free questions with answers, explanations and the source for each. Answer one to see why. No sign-up.

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  1. 1 / 60

    Under the 2023 NEC (2025 CEC), when an equipment manufacturer provides a specific tightening value for a termination, how must that torque be applied?

  2. 2 / 60

    Using full-load line current = volt-amperes ÷ (1.732 × line volts), a 30,000 VA (30 kVA), 480 V three-phase transformer has a full-load line current of:

  3. 3 / 60

    You are connecting deenergized equipment to an energized circuit by means of a conducting wire. Under T8 2320.2(b), you shall first attach the wire to:

  4. 4 / 60

    Using kVA = 1.732 × volts × amperes ÷ 1,000, a 208 V three-phase load drawing 100 A per phase is:

  5. 5 / 60

    Under 430.52(B), the motor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the motor's:

  6. 6 / 60

    A motor nameplate must show a time rating. Under 430.7(A), the time rating shall be:

  7. 7 / 60

    A breaker trips because a drywall screw pierced a cable and caused a short circuit. Under the Article 100 definition of overload, a fault such as a short circuit or ground fault is:

  8. 8 / 60

    Work on exposed energized parts has been approved. Under T8 2320.2, approved insulated gloves shall be worn for voltages in excess of how many volts to ground?

  9. 9 / 60

    The equipment grounding conductor connects to the ___ screw:

  10. 10 / 60

    A time-delay (dual-element) fuse chosen from Table 430.52(C)(1) is not sufficient for the starting current of the motor. Under 430.52(C)(1)(b), its rating may be increased, but the increased rating is capped at what percent of the full-load current?

  11. 11 / 60

    Three single-phase transformers are connected as a three-phase bank operating as a unit. For overcurrent protection under 450.3, the word transformer means:

  12. 12 / 60

    A motor overload relay protects against:

  13. 13 / 60

    Using Ohm's law in the form I = E ÷ R, a 120 V circuit with a 10-ohm load draws a current of:

  14. 14 / 60

    Motor running overload protection guards mainly against:

  15. 15 / 60

    A motor drives a process where immediate automatic shutdown on overload would add hazards to persons, and continued operation is needed for a safe shutdown. Under 430.44, the motor overload sensing device is permitted to be connected to:

  16. 16 / 60

    Conductors supplying several motors serve three motors with full-load current ratings of 40 A, 20 A, and 10 A and no other load. Using 430.24, the conductors shall have an ampacity not less than:

  17. 17 / 60

    Motor branch-circuit conductors (continuous duty) must be sized at least ___ of the motor full-load current:

  18. 18 / 60

    A dead kitchen circuit turns out to be a tripped GFCI receptacle hidden behind a refrigerator. Under 406.4(D), on replacement of receptacles, AFCI-type and GFCI-type receptacles shall be installed in:

  19. 19 / 60

    Resistances in series add. Three 30-ohm resistors in series total:

  20. 20 / 60

    That GFCI-type receptacle on the ungrounded two-wire circuit also feeds several downstream outlets. Under 406.4(D)(2)(b), what shall not be connected from the GFCI-type receptacle to any outlet supplied from it?

  21. 21 / 60

    Per NEC/CEC 200.10, if the grounded-conductor terminal on a receptacle is not visible for direct identification, how must that termination point be identified?

  22. 22 / 60

    A breaker opened on overcurrent and you must find out why. Under the T8 Electrical Safety Orders definition, an overcurrent may result from:

  23. 23 / 60

    Using P = E × I, a 277 V lighting load that draws 5 A uses a power of:

  24. 24 / 60

    You will work on a de-energized motor drive that contains capacitors. Before the work, T8 2320.4 makes an authorized person responsible for:

  25. 25 / 60

    Tracing a dead circuit, you find its panelboard inside a bedroom clothes closet. Under 240.24(D), overcurrent protective devices shall not be located:

  26. 26 / 60

    Using I = P ÷ E, a 120 V, 1200 W heater draws a current of:

  27. 27 / 60

    Before choosing a replacement breaker, you ask the engineer about fault current at the panel. Under Article 100, fault current is the current delivered at a point on the system:

  28. 28 / 60

    Checking polarity on a new receptacle, you look for the terminal intended for connection to the grounded conductor. Under 200.10(B)(1), it shall be identified by a metal or metal coating that is white or silver in color, or by:

  29. 29 / 60

    A GFCI trips on a leakage current far too small to trip the 20 A breaker feeding it. Under the T8 definition, a GFCI de-energizes the circuit when a current to ground goes above a predetermined value that is:

  30. 30 / 60

    An AFCI is designed to detect:

  31. 31 / 60

    NEC/CEC 110.15 requires the high leg of a 4-wire delta system to be permanently identified. Which color is specified for that identification?

  32. 32 / 60

    A GFCI holds on a circuit whose normal leakage current is 3 mA. Per the Article 100 note, Class A ground-fault circuit interrupters do not trip when the ground-fault current is:

  33. 33 / 60

    You clamp an ammeter on a parking-lot lighting circuit that stays at full current all night. Under the Article 100 definition, a continuous load is a load where the maximum current is expected to continue for:

  34. 34 / 60

    An authorized person is getting ready for work on de-energized electrical equipment that is still connected to the wiring system. Under T8 2320.4, which step is that person responsible for before the work?

  35. 35 / 60

    Using full-load line current = volt-amperes ÷ (1.732 × line volts), a 75,000 VA (75 kVA) transformer with a 208 V three-phase secondary has a full-load secondary line current of:

  36. 36 / 60

    The grounded (neutral) conductor connects to the ___ screw:

  37. 37 / 60

    Under 430.32(A)(1), a separate overload device for a continuous-duty motor with a marked temperature rise of 40°C or less is selected to trip at, or rated at, what percent of the motor nameplate full-load current rating?

  38. 38 / 60

    Using P = I × I × R, the power dissipated by a 20-ohm resistor carrying 3 A is:

  39. 39 / 60

    Fuses are used for motor overload protection on a 3-wire, 3-phase ac supply system with one conductor grounded. Under 430.36, a fuse shall be inserted in:

  40. 40 / 60

    Under NEC/CEC 250.126, an equipment-grounding terminal screw on a wiring device is identified as green and typically has what distinctive physical feature?

  41. 41 / 60

    A large service main opens on its ground-fault protection of equipment (GFPE) even though no conductor is overloaded. Under Article 100, GFPE is a system intended to protect equipment from:

  42. 42 / 60

    Verifying phase identification in a new panelboard, you check the bus order. Under 408.3(E)(1), ac phase arrangement on 3-phase buses shall be A, B, C:

  43. 43 / 60

    To find the breaker for a dead bedroom circuit, you read the panel directory. Under 408.4(A), every circuit and circuit modification shall be provided with a description that is:

  44. 44 / 60

    In an older building you find gray conductors landed on breakers. The informational note to 200.10(D) warns that the color gray:

  45. 45 / 60

    Using kVA = volts × amperes ÷ 1,000, a 240 V single-phase load drawing 50 A is:

  46. 46 / 60

    A transformer’s disconnecting means is in a remote location, out of sight of the transformer. Under 450.14, the disconnecting means shall be lockable open and its location shall be:

  47. 47 / 60

    A pendant lampholder comes with attached leads, and you must land them with correct polarity. Under 200.10(D), the conductor attached to the screw shell shall have:

  48. 48 / 60

    You are disconnecting equipment from an energized circuit that is connected by means of a conducting wire. Under T8 2320.2(b), you shall remove:

  49. 49 / 60

    Under Title 8 Section 2320.3, all electrical equipment and systems shall be treated as ___ until tested or otherwise proven to be de-energized:

  50. 50 / 60

    A 480-volt motor has a full-load current rating of 52 A. Using 430.110(A), its disconnecting means shall have a current rating not less than:

  51. 51 / 60

    Separate motor overload protection is sized from the motor's:

  52. 52 / 60

    A ground fault at a bathroom receptacle sends current to ground. Per the Article 100 note, which Class A device trips when the ground-fault current is 6 mA or higher?

  53. 53 / 60

    Using turns ratio = primary voltage ÷ secondary voltage, stepping 480 V down to 120 V requires a transformer with a turns ratio of:

  54. 54 / 60

    You are checking the branch-circuit conductors for a motor built for low speeds (less than 1200 RPM). Under 430.6(A)(2), the ampacity of its conductors is determined from:

  55. 55 / 60

    Using R = E ÷ I, a 208 V load that draws 8 A has a resistance of:

  56. 56 / 60

    For equal resistors in parallel, total resistance = one resistor ÷ the number of resistors. 3 resistors of 30 ohms each in parallel total:

  57. 57 / 60

    An electrician will troubleshoot within reaching distance of exposed energized parts. Under T8 2320.7(d), the employer shall ensure the employee removes:

  58. 58 / 60

    You need to confirm the rating of the breaker feeding a dead 20 A circuit. Under 240.83(B), circuit breakers rated at 100 amperes or less and 1000 volts or less shall have the ampere rating molded, stamped, etched, or similarly marked into:

  59. 59 / 60

    A Class A ground-fault circuit interrupter is designed to trip when the ground-fault current is:

  60. 60 / 60

    In the 2023 NEC, where can a technician find default tightening torque values for terminations when the installation instructions or product markings do not provide one?

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