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Electricity - USCG Exam Questions

Marine electrical systems: motors and generators, switchboards and distribution, batteries, electronics, and control engineering.

Every question below is a real U.S. Coast Guard exam question with four choices. Answer one and the correct choice is revealed instantly, with the USCG reference and illustration where the question uses one.

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All Electricity questions

Questions 1–100 of 1,595 · page 1 of 16

  1. #1 Which of the following statements is true concerning the operating characteristics of a basic squirrel-cage induction motor?
  2. #2 How is the speed of a squirrel-cage induction motor determined?
  3. #3 In a three-phase, squirrel-cage type, and induction motor, how is the primary rotating magnetic field established?
  4. #4 Which of the illustrated motors has a totally enclosed, fan-cooled (TEFC) motor enclosure? Illustration EL-0001 illustration
  5. #5 Which of the pictured motors is a square core shaded pole motor used to drive very small electrical loads and is non-reversible. Illustration EL-0208 illustration
  6. #6 One item listed on the name plate of a cargo pump motor is 'degrees centigrade rise.' What does the number stamped for this item represent?
  7. #7 How is the full-load (rated) torque of an induction motor defined?
  8. #8 What type of motor is illustrated by the schematic of figure "B" of the illustration and what type of starting relay is used? EL-0209 illustration
  9. #9 With respect to electrical enclosure types, how may an electric motor be designed and constructed?
  10. #10 What will be the impact of reduced voltage applied to an AC induction motor during the starting period?
  11. #11 In general, what type of starter would be used to connect polyphase induction motors to full line voltage at the instant of start-up?
  12. #12 How is the difference between the synchronous speed of a three phase induction motor and its operating speed correctly expressed?
  13. #13 Assuming that the 3-phase power source has a phase sequence of A-B-C and that the motor is connected as shown in figure "A", if the motor has a counte... illustration
  14. #14 Auto-transformer starters, sometimes called starting compensators, are sometimes used with larger polyphase induction motors. What function do they pe...
  15. #15 As shown in the two-speed single winding three phase motor connection diagrams illustrated in figure "B", what is the connection scheme associated wit... illustration
  16. #16 The torque-speed and current-speed curves for a three-phase induction motor with a squirrel cage rotor are shown in figures "A" and "B" of the illustr... illustration
  17. #17 Which of the following statements describes what will occur if the motor torque-speed and current-speed curves shown in the illustration is required t... illustration
  18. #18 According to the sample sheet of a typical "List of Motors and Controls" as shown in the illustration, which of the following motor applications featu... illustration
  19. #19 Which of the pictured motors within the split phase family of single phase induction motors represents a capacitor start, induction run motor? Illustr... illustration
  20. #20 What is the main function in the use of a capacitor for starting a single phase motor?
  21. #21 Within the split phase family of single phase motors, what are the operational characteristics of the motor shown in figure "B" of the illustration? I... illustration
  22. #22 As shown in figures "A", "B", "C", and "D" of the illustration, what is the usual means by which the rotation direction of the motor is reversed? Illu... illustration
  23. #23 What are the operational characteristics of the split phase motor shown in figure "B" of the illustration? Illustration EL-0215 illustration
  24. #24 Of the following listed single-phase induction motors, which has the highest starting torque?
  25. #25 What is the main purpose of the auxiliary winding on a split-phase, single-phase motor?
  26. #26 What type of rotor is used in the split-phase family of single-phase motors?
  27. #27 Which statement is true concerning a split-phase induction motor?
  28. #28 A shaded-pole motor is a specific type of motor included in what class of motor?
  29. #29 Universal motors will operate on AC or DC current. In what application is this type of motor generally?
  30. #30 An increase in which of the listed conditions will increase the speed of a synchronous electric motor?
  31. #31 What causes the rotor of a synchronous motor to operate in synchronism with the rotating field?
  32. #32 What is the function of the squirrel cage windings installed on a synchronous motor rotor?
  33. #33 What is the most common source of excitation for the rotor of a synchronous motor?
  34. #34 What is the purpose of the squirrel-cage windings included as part of a synchronous motor?
  35. #35 For what purpose is the variable resistance placed in the rotor circuit of a wound-rotor induction motor provided?
  36. #36 As shown in the illustrated wound-rotor induction motor how is the direction of rotation of the motor reversed? Illustration EL-0148 illustration
  37. #37 What is the characteristic of a wound-rotor induction motor, with a high resistance inserted in series with the rotor winding at startup?
  38. #38 What is the characteristic of an wound rotor induction motor with maximum rheostat resistance inserted in the rotor circuit during starting?
  39. #39 9. When performing routine A.C. motor maintenance what should be included?
  40. #40 When performing routine A.C. motor maintenance what should be included?
  41. #41 What is a useful instrument for checking 3 phase A.C. motor performance by measuring possible unbalanced currents?
  42. #42 For what reason should engine room watch standers keep a constant check on the loads carried by electric motors?
  43. #43 Which of the following statements represents the FIRST step in seating new brushes on slip rings?
  44. #44 By periodically checking the stator-to-rotor air gap clearance in an induction motor with a feeler gauge, what is prevented?
  45. #45 A digital multimeter is set up as shown in the illustration to evaluate the single-circuit stator windings of a squirrel cage induction three-phase mo... illustration
  46. #46 What would be the effect of carrying field excitation excessively high on a synchronous motor?
  47. #47 A single-phase capacitor-start induction motor starts, comes up to about 75% rated speed, slows down to a lower speed, and accelerates again. Where is...
  48. #48 If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in opera...
  49. #49 Which of the following methods should be used to test for an 'open' stator winding coil in a wye-connected AC squirrel cage induction motor?
  50. #50 If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, what will be the result?
  51. #51 1. (1.1.1.As shown in figure "B" of the illustration, with a digital multimeter set up as an ohmmeter, what set of readings would be consistent with a... illustration
  52. #52 The leads from a ohmmeter are attached to the leads of the opposite ends of an AC motor stator field coil. If a reading of infinity is obtained, what...
  53. #53 If a single-phase capacitor start induction motor fails to start, but instead hums without starting, what is most likely to be the problem?
  54. #54 In testing a three-phase delta-connected winding for an open circuit using a ohmmeter, what must be done?
  55. #55 When testing the rotor of a synchronous motor for short circuits, a low voltage source is applied across the rotor coils through the collector rings....
  56. #56 In using a portable growler for the purpose of locating a shorted stator coil in an AC motor as shown in the illustration, what statement is true as t... illustration
  57. #57 When troubleshooting AC motors, what can a portable growler be used to locate?
  58. #58 Which of the listed instruments can be best used to locate a grounded field coil in a synchronous motor onboard ship?
  59. #59 How does the resistance of a conductor vary?
  60. #60 In a three-phase circuit, how far apart are the phase voltages?
  61. #61 AC circuits can possess characteristics of resistance, inductance, and capacitance. In terms of units of measure, how is the capacitive reactance of t...
  62. #62 AC circuits may develop resistance, inductance, and capacitance. What is the unit of measure used to express inductive reactance?
  63. #63 An electrical connection between the wiring of an electric motor and its metal frame is known as what?
  64. #64 An accidental path of low resistance which bypasses the intended resistance and passes an abnormal amount of current is known as what?
  65. #65 A direct current passing through a wire coiled around a soft iron core is known as what?
  66. #66 The device that most commonly utilizes the principle of electromagnetic induction by mutual inductance is what?
  67. #67 The number of cycles per second occurring in AC voltage is known as what characteristic?
  68. #68 Electric current is the flow of electrons through a conductor. How is the rate of this flow measured?
  69. #69 What happens to the current in a series circuit when the voltage remains constant and the resistance increases?
  70. #70 Which of the following statements is correct for the illustrated circuit in figure "B"? Illustration EL-0020 illustration
  71. #71 Consider a series circuit employing two resistors. What is true about the resistance value of the second resistor compared to the first when the volta...
  72. #72 What statement is true concerning the total power consumed in a series circuit?
  73. #73 What is true concerning all of the connecting conductors of a DC series circuit?
  74. #74 Which of the following statements concerning a circuit with parallel connected resistors is correct?
  75. #75 Which of the following statements is true concerning circuits with parallel connected resistances?
  76. #76 What is statement is true concerning the total resistance of a parallel circuit?
  77. #77 What statement is true concerning the electrical diagram shown in figure "B" of the illustration? Illustration EL-0019 illustration
  78. #78 What would be the total capacitance of the circuit illustrated in figure "A" if the value of capacitor C1 was 100 microfarads and capacitor C2 was 50... illustration
  79. #79 Which of the electrical properties listed will always be the same across each component in a parallel circuit?
  80. #80 What will happen to the total circuit resistance when additional parallel circuits are added to a circuit?
  81. #81 As shown in figure "A" of the illustration, with the switch closed what statement is true if 'R1' and 'R2' have unequal resistance values? Illustratio... illustration
  82. #82 Four lamps are connected in parallel in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
  83. #83 Which statement is true concerning the total power consumed in a parallel circuit?
  84. #84 In a conventional AC generator utilizing brushes, direct current from the exciter output is passed through the windings of the main field rotor by wha...
  85. #85 Compared to conventional alternators, brushless alternators are designed to operate without the use of what?
  86. #86 Which of the following statements is true concerning all rotating-field three-phase alternators?
  87. #87 Why are space heaters provided on larger generators?
  88. #88 Of the listed factors that influence the amount of RMS voltage induced in the windings of an AC generator operating at a constant 60 Hz frequency, whi...
  89. #89 By what means is voltage and current generated by modern revolving field AC generators brought out from the alternator enclosure to the connected swit...
  90. #90 What is the most common type of AC service generator found aboard ship in terms of armature and field types?
  91. #91 How are AC and DC generators are similar?
  92. #92 By what means is a diesel driven emergency generator prevented from being paralleled with the ship's service generators?
  93. #93 As shown in the illustration, which brush holder would be appropriate to use in a bi- directional motor? Illustration EL-0029 illustration
  94. #94 Upon failure of the ships normal electrical power supply, by means of what device does the emergency generator supply power to the emergency switchboa...
  95. #95 What is the main purpose of an electric space heater installed in a large AC generator?
  96. #96 When shore power is being connected to a ship in dry dock, what must be ensured, assuming that the ship's generators are rated at 450 VAC, 60Hz with a...
  97. #97 With what device is the RPM of an AC generator indirectly measured on a switchboard when operating singly (no other generator connected to the bus)?
  98. #98 What does the amount of voltage induced in the stator windings of a modern AC generator mainly dependent upon?
  99. #99 A DC generator which is used to supply direct current in order to provide magnetizing current to an AC generator field is commonly known as what?
  100. #100 In which figure shown in the illustration will the highest voltage be induced? Illustration EL-0028 illustration

Electricity questions: what to expect

Q How many Electricity questions are in the Engine pool?

There are 1,595 Electricity questions on this site, every one released by the U.S. Coast Guard or taken from the National Maritime Center's sample examinations, with its correct answer. The exam draws its Electricity module from the same pool.

Q What score do I need to pass the Electricity module?

Most USCG exam modules, including Electricity, require 70 percent to pass. Rules of the Road modules require 90 percent.

Q Are these the real USCG Electricity exam questions?

Yes. They are the published U.S. Coast Guard questions, matched to the National Maritime Center's 2026 sample examinations. Answer any question to see the correct choice, the USCG reference and the illustration where the question uses one.

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