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Engine · 1,595 questions

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 501–600 of 1,595 · page 6 of 16

  1. #502 The set point current at which a magnetic-type overload relay tends to trip may be increased by turning the dashpot in the 'lower' direction. What eff...
  2. #503 Which of the following methods should be used to dress the face of silver-plated contacts?
  3. #504 Grease coatings on electrical contact surfaces increase contact resistance. How should grease accumulations be removed?
  4. #505 Which of the following statements is true concerning the cleaning of electrical contacts?
  5. #506 What item (or items) constitute routine AC motor controller maintenance?
  6. #507 Using the illustrated catalog number selection chart, determine the correct catalog number for a motor starter that meets the following selection crit... illustration
  7. #508 Which device will stop the motor shown in the illustration in case of a short-circuit (high current) motor fault? Illustration EL-0080 illustration
  8. #509 If you hear a loud buzzing noise coming from a magnetic motor controller, what should you do?
  9. #510 The motor fails to start on an attempted startup. With the start button depressed, a voltmeter reading between 1 and 5, as illustrated in figure "A",... illustration
  10. #511 Why are motor controllers seldom troubled by grounds?
  11. #512 The motor starts when the start button in the illustration is pushed, but stops when the button is released. What is most likely the trouble? Illustra... illustration
  12. #513 What can be the cause of excessive heat or burning contacts in an operating motor controller?
  13. #514 The illustrated motor fails to start and gives a loud hum when the start button is depressed, what should then be your first action? Illustration EL-0... illustration
  14. #515 In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 5 reads line voltage, while the voltmeter reading bet... illustration
  15. #516 If the motor shown in the illustration will not start when the "off-run" switch is placed in the run position, which of the listed components should b... illustration
  16. #517 When troubleshooting a motor controller, all indications are that a relay coil should be energized. If there was no magnetic pull, with rated voltage...
  17. #518 When troubleshooting a magnetic controller, it is found that the contacts are welded together. What is the most probable cause?
  18. #519 As shown in figure "A" and "B" of the illustration, the potable water pump is short cycling by the action of the pressure switch as a result of an unu... illustration
  19. #520 If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, what is the probable cause?
  20. #521 A loud buzzing noise coming from the contacts in a magnetic controller can be caused by what condition?
  21. #522 As shown in figure "A" of the illustration, if in troubleshooting the control circuit using on-line techniques with a voltmeter with the start button... illustration
  22. #523 If a digital multimeter is set up as shown in figure "A" of the illustration to test an AC contactor coil, what would the display read if the coil is... illustration
  23. #524 What can cause the pitting or welding of controller contacts?
  24. #525 If many turns of an alternating current coil for a contactor become short circuited, what will happen to the coil?
  25. #526 At a minimum threshold, how many milliamps of current through the body produces a painful sensation that most people would perceive as an electric sho...
  26. #527 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would be unable to let go of the energiz...
  27. #528 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would experience respiratory paralysis a...
  28. #529 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would suffer ventricular fibrillation an...
  29. #530 With all other factors considered equal (such as voltage, conducting path through the body and the duration of contact), contact with an energized ele...
  30. #531 Before electrical work can be safely undertaken, the equipment must be de-energized, locked and tagged out, and verification must be made that the cir...
  31. #532 Which of the following devices would be forbidden to use as a primary means of electrical isolation?
  32. #533 Which of the following voltage testers would be associated with high quality, be safe to use, and minimize the electric shock hazard?
  33. #534 What is the primary means by which an electrical maintenance worker is protected from electrical hazards while performing work on an electrical circui...
  34. #535 After prior isolation and lockout/tagout procedures are performed, which electrical device requires discharging any stored electrical energy before an...
  35. #536 AC circuits can possess characteristics of resistance, inductance, and capacitance. In terms of units of measure, how is the capacitive reactance of t...
  36. #537 The root mean square (RMS) value of a sine-wave current may also be expressed as what value?
  37. #538 For the purpose of calculating apparent power, which of the following procedures should be used to determine the total load current of a three-phase,...
  38. #539 If the voltage and the current developed in an AC circuit reach their peak values at the same time (with a phase angle difference of zero), what is th...
  39. #540 An accidental path of low resistance bypassing the intended path and allowing passage of an abnormally high amount of current is known as what?
  40. #541 In the flow of one cycle of single phase alternating current past any given point in a circuit, how many times will the current peak to a maximum?
  41. #542 What is the opposition to the establishment of magnetic lines of force in a magnetic circuit called?
  42. #543 In terms of load type, in what type of alternating current circuit will the voltage always lead the current?
  43. #544 How may the unit "hertz" be best described?
  44. #545 What will happen to an electrical coil when the direct current flowing through the coil is increasing?
  45. #546 18 August 2014 --------------------------------------- 119 United States Coast Guard Electrical-Electronics-Control Engineering National Maritime Cent... illustration
  46. #547 In a series circuit what is the total applied voltage equal to?
  47. #548 In a series circuit, which value will remain unchanged at all places in the circuit?
  48. #549 Referring to figure "B" of the illustration, what statement is true? EL-0020 illustration
  49. #550 Referring to figure "B" of the illustration, what statement is true? EL-0020 illustration
  50. #551 Four lamps are connected in series in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
  51. #552 Which of the following statements concerning a circuit with parallel connected resistors is correct?
  52. #553 Which of the following statements is true concerning circuits with parallel connected resistances?
  53. #554 What statement is true concerning the total resistance of a parallel circuit?
  54. #555 What statement is true concerning the electrical diagram shown in figure "B" of the illustration? EL-0019 illustration
  55. #556 Four lamps are connected in parallel in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
  56. #557 Which statement is true concerning the total power consumed in a parallel circuit?
  57. #558 Which of the electrical properties listed will always be the same across each component in a parallel circuit?
  58. #559 What will happen to the total circuit resistance when additional parallel circuits are added to a circuit?
  59. #560 As shown in figure "A" of the illustration, with the switch closed what statement is true if 'R1' and 'R2' have unequal resistance values? EL-0019 illustration
  60. #561 In a simple DC circuit, the resistance is held constant while the applied voltage is halved. What will be the effect on the current flow as compared t...
  61. #562 An electrical component is connected across a 120 volt 60 hertz AC supply. What is the current drawn by the component if the impedance is 200 ohms?
  62. #563 In a 60 Hz AC system, what is the duration in seconds for one complete cycle?
  63. #564 An AC generator produces 60 Hz at 1800 RPM. If the generator speed is increased to 1830 RPM, what will happen to the frequency in Hz?
  64. #565 How is the power dissipated as heat in a direct current circuit calculated?
  65. #566 A 125 volt DC motor is rated at 10 kW. What is the current rating of the motor?
  66. #567 What is the total resistance of figure "B" of the illustrated circuit if the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 illustration
  67. #568 What is the total resistance of the electrical circuit illustrated in figure "B" if the resistance of R1 is 2 ohms, R2 is 4 ohms, and R3 is 4 ohms and... illustration
  68. #569 In the illustration, 1, 2, 3 and 4 are 12 volt batteries. What will be the nominal voltage as read by a voltmeter across the output of the battery ban... illustration
  69. #570 If the supply voltage is 220 volts 60 Hz, what is the operating voltage of the motor controller control circuit illustrated in figure A of the illustr... illustration
  70. #571 What will be the total current in figure "B" of the illustrated circuit with the switch closed if the applied voltage is 24 volts and the resistance o... illustration
  71. #572 In figure "A" of the illustration, 12 volts is applied to the circuit where the resistance of R1 is 10 ohms and R2 is 10 ohms. what is the voltage acr... illustration
  72. #573 As shown in figure "A" of the illustration, what would be the circuit impedance if the capacitive reactance is 10 ohms and the resistance is 10 ohms?... illustration
  73. #574 In the schematic of the electrical circuit shown in figure "A" of the illustration, what is the value of the total capacitance, when compared to the v... illustration
  74. #575 An AC circuit has a capacitive reactance of 30 ohms in addition to an inductive reactance of 40 ohms connected in series. What is the total reactance...
  75. #576 Two 100 watt light bulbs rated at 100 volts are connected in parallel across a 100 volt power supply. What will be the total power consumed by the two...
  76. #577 If a circuit has resistances of 5, 10, and 20 ohms connected in parallel, what is the combined total resistance of the circuit?
  77. #578 In the schematic of the electrical circuit shown in figure "A" of the illustration, what is the value of the total capacitance, when compared to the v... illustration
  78. #579 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 200... illustration
  79. #580 What would be the total current in figure "A" of the circuit illustrated if the value of capacitor C1 was 100 microfarads, capacitor C2 was 200 microf... illustration
  80. #581 What would be the capacitive reactance of the circuit shown in figure "A" of the illustration if the capacitance of C1 was 100 microfarads, the capaci... illustration
  81. #582 What is the current flowing through R3 in figure "B" of the illustrated circuit when the switch is closed if the battery voltage is 12 VDC and resista... illustration
  82. #583 What would be the voltage drop across the parallel branches of the circuit shown in figure "B" of the illustration if the source voltage is 30 volts,... illustration
  83. #584 What would be the voltage drop across the series string of the circuit shown in figure "A" of the illustration if the source voltage is 30 volts, the... illustration
  84. #585 What would be the total current draw of the circuit as shown in figure "A" of the illustration if the source voltage is 24 volts, the resistance for R... illustration
  85. #586 What would the total power consumed by the circuit as shown in figure "A" of the illustration if the source voltage is 12 volts, the resistance for R1... illustration
  86. #587 What would the total power consumed by the circuit as shown in figure "B" of the illustration if the source voltage is 12 volts, the resistance for R1... illustration
  87. #588 The turns ratio of the tapped step down transformer shown in figure "C" of the illustration is four to one and all taps are equally spaced. If 440 vol... illustration
  88. #589 The turns ratio of the tapped step down transformer shown in figure "C" of the illustration is four to one and all taps are evenly spaced. If 120 volt... illustration
  89. #590 In figure "1" of the diagram shown in the illustration, the three phase step down power transformer has a turns ratio of four to one. If a three-phase... illustration
  90. #591 In figure "2" of the diagram shown in the illustration, the three phase step down power transformer has a turns ratio of four to one. If a three-phase... illustration
  91. #592 In figure "4" of the diagram in the illustration, the three phase step down power transformer has a turns ratio of five to one. If a three-phase 4160... illustration
  92. #593 A simple, untapped, single-phase 480/120 VAC step-down control transformer is rated at 600VA at 60 Hz. Neglecting power factor, what is the rated seco...
  93. #594 What would be the synchronous speed of an eight-pole three-phase squirrel-cage induction motor operating at 60 Hz?
  94. #595 What would be the synchronous speed of a 24-pole three-phase synchronous motor operating at 20 Hz?
  95. #596 What would be the actual rotor speed for a 4-pole three-phase squirrel-cage induction motor operating at 60 Hz if the rotor slip is 3%?
  96. #597 If a 12-pole three-phase synchronous alternator is operating at 590 rpm, what will be its output frequency?
  97. #598 A six-pole three-phase squirrel-cage induction motor operating at 60 Hz is running at 1155 rpm. What is the percentage slip in this case?
  98. #599 Which figure shown in the illustration represents the schematic symbol shown in figure "2"? EL-0034 illustration
  99. #600 As shown in the illustrated devices and symbols, which of the symbols shown in the illustration represents a standard normally closed relay contact? E... illustration
  100. #601 Which of the electronic schematic symbols represents the capacitor illustrated in figure 1 of the illustration? Illustration EL-0015 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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The Engine pool holds the current U.S. Coast Guard questions for engineering credentials, from QMED ratings through DDE and Assistant Engineer up to Chief. Answer any question to see the correct choice instantly.