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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 301–400 of 1,595 · page 4 of 16

  1. #301 Which of the illustrated schematic symbols represents the type of switch pictured in figure "F" of the illustration? Illustration EL-0026 illustration
  2. #302 Which electrical schematic symbol represents a normally open thermostat? Illustration EL-0059 illustration
  3. #303 Which of the electrical schematic symbols represents a normally open limit switch? Illustration EL-0059 illustration
  4. #304 What is statement is true in reference to reading electrical motor controller elementary diagrams?
  5. #305 What type of electrical diagram is shown in figure "B" of the illustration? Illustration EL-0007 illustration
  6. #306 The electrical diagram shown in figure B of the illustration represents what type of DC motor? Illustration EL-0054 illustration
  7. #307 Which of the following statements concerning electrical cables is correct?
  8. #308 Why are large cable sizes often formed as individual conductors comprised of several smaller strands?
  9. #309 The 24 volt DC bus on the emergency switchboard is used to supply power to what system or equipment?
  10. #310 What is a common type of protective covering used on electrical conductors?
  11. #311 What is the reason that some electric cables are formed of stranded wire?
  12. #312 In the illustrated one line diagram, if the ship's service generator on line fails, what statement is true concerning the operation of the emergency d... illustration
  13. #313 As shown in figure "B" of the illustration, with respect to the common equipment grounding conductor, what statement is true? Illustration EL-0125 illustration
  14. #314 As shown in the illustration, which of the following pieces of equipment is provided with a remote pushbutton station? Illustration EL-0165 illustration
  15. #315 As shown in the illustrated one-line diagram of a two-tiered emergency power system for a passenger ship, what statement is true? Illustration EL-0166 illustration
  16. #316 Which of the illustrated safety disconnect switches represents a double throw switch? Illustration EL-0176 illustration
  17. #317 Why is copper often used as an electrical conductor?
  18. #318 Which of the following characteristics is most critical in determining the wire gauge size of the cable to be used in a particular circuit?
  19. #319 What is the characteristic that is associated with an "instantaneous-trip" single- element type fuse?
  20. #320 How would a circuit with a blown fuse be described?
  21. #321 For what purpose are time delayed or delayed action-type fuses used?
  22. #322 Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced?
  23. #323 How are fuses rated?
  24. #324 In a dual element time-delay cartridge-type fuse, what type of protection is provided for motor applications?
  25. #325 By what means does a molded-case circuit breaker provide protection against short circuits?
  26. #326 How will a molded-case circuit breaker with a thermal trip unit react immediately after it has tripped, as a result of an overloaded motor circuit?
  27. #327 How can a motor be protected from overheating due to sustained motor overload?
  28. #328 In figure "1" of the illustration, what are the trip characteristics associated with this type of circuit breaker? Illustration EL-0033 illustration
  29. #329 By what means is protection against sustained overloads occurring in molded-case circuit breakers provided?
  30. #330 The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts. How is this done?
  31. #331 When the operating handle of a molded-case circuit breaker is in the mid-position, what is the indication for the position of the circuit breaker?
  32. #332 A thermal-magnetic circuit breaker for a 300 KW alternator is rated at 500 amperes at full continuous load. Which of the following conditions will tri...
  33. #333 How does a circuit breaker differ from a fuse?
  34. #334 Under voltage trips are frequently installed on switchboard circuit breakers for what reason?
  35. #335 How is electrical conductor insulation classed? Example: insulation class H
  36. #336 Which of the following materials is a good electrical insulator?
  37. #337 As shown in the illustration, what event would give the same indication that would occur when a stern light circuit fuse blows open? Illustration EL-0... illustration
  38. #338 What is the purpose of the capacitor within component "5" of the circuit shown in figure "B" of the illustration? Illustration EL-0081 illustration
  39. #339 What type of circuit is represented by the diagram shown in the illustration? Illustration EL-0058 illustration
  40. #340 A shown in the illustration, which of the lighting fixtures represents an incandescent bulb? Illustration EL-0122 illustration
  41. #341 Besides the fluorescent lamp itself and possibly a starter, which of the following components is included in a fluorescent lighting fixture?
  42. #342 Which of the listed types of lighting fixtures does the diagram shown in figure "A" of the illustration represent? Illustration EL-0081 illustration
  43. #343 What is the functional purpose component "5" as shown in figure "B" of the illustration? Illustration EL-0081 illustration
  44. #344 Incandescent lamps are classified according to the shape of the bulb and the type of service, as well as the size and style of the base. How are incan...
  45. #345 As shown in the illustration, the change-over switch is what type of device? Illustration EL-0058 illustration
  46. #346 As shown in the illustration, what are the characteristics of the trouble relay contacts? Illustration EL-0058 illustration
  47. #347 When will the timer element of a reverse power relay activate the relay?
  48. #348 Which of the following represents a characteristic of an ungrounded electrical distribution system?
  49. #349 What is a wattmeter used to measure and indicate?
  50. #350 The true power indicated by a wattmeter depends on the current flow through the load, the magnitude of the voltage across the load, and what other fac...
  51. #351 What is a bus disconnect link used to isolate?
  52. #352 Capacitors can be used in electric distribution systems to improve power factor. This is accomplished by seesawing energy between the capacitor and wh...
  53. #353 Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured?
  54. #354 What is meant by a 'dead front' switchboard?
  55. #355 What is a purpose of the automatic bus transfer device shown in the illustration? Illustration EL-0014 illustration
  56. #356 In comparison to a main switchboard for a DC electrical distribution system, a main switchboard for an AC electrical distribution system requires the...
  57. #357 What statement is true concerning a ground in an 450 VAC electrical circuit outside the engine room?
  58. #358 How are the line losses in a distribution circuit kept to a minimum?
  59. #359 What is the name of the part of the shipboard electrical system used to control the distribution of power to the branch circuits?
  60. #360 Which of the following is a pictured three phase power transformer, usually used to step down line voltage for supplying reduced voltage lighting circ... illustration
  61. #361 When a low input voltage is delivered to a transformer which then produces a high output voltage, what is the proper name for the transformer type?
  62. #362 Which of the following statements is true concerning step-down transformer operation?
  63. #363 What will happen to the primary winding when the load increases on the secondary windings of a transformer?
  64. #364 When a transformer is used to step down voltage, what statement is true?
  65. #365 Which of the following statements describes the difference between the primary windings and the secondary windings of a 2:1 step-down voltage transfor...
  66. #366 What is the primary purpose associated with the use of transformers onboard ships with AC generators?
  67. #367 Which of the listed figures shown in the illustration represents a three phase transformer connected in a wye-delta configuration? Illustration EL-008... illustration
  68. #369 What is the basic operating principle of a transformer in terms of producing a voltage?
  69. #370 When working on a high voltage circuit, you should always have another person present with you. This person should have a good working knowledge of th...
  70. #371 What is the proper way to apply plastic electrical tape to an electric cable splice?
  71. #372 When working on electrical circuits containing large capacitors, in addition to de- energizing the circuit, which of the listed precautions should als...
  72. #373 Which of the following statements represents the FIRST precaution to be taken prior to working on any installed electrical component?
  73. #374 When changing fuses, what safety precaution should be taken?
  74. #375 When replacing fuses, what practice should be observed?
  75. #376 What device can be used to check the calibration of a circuit breaker?
  76. #377 What should be done when performing maintenance of circuit breaker contacts?
  77. #378 As shown in the illustration, what maintenance would be required of the circuit components? Illustration EL-0058 illustration
  78. #379 In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. How is this accomplished?
  79. #380 What should be included in the performance of routine maintenance of dry-type transformers?
  80. #381 When replacing a defective transformer in a paralleled transformer configuration, which of the following actions must be carried out to insure proper...
  81. #382 When maintenance personnel are working on electrical equipment, all supply switches should be secured in the open position and tagged. Who specificall...
  82. #383 Why must accidental grounds in a shipboard electrical system must be repaired as soon as possible?
  83. #384 The FIRST requirement for logical troubleshooting of any system requires the troubleshooter to do what?
  84. #385 Multiple grounds have developed and were initially indicated by the ground- detecting system as one ground. What is the FIRST step in locating the gro...
  85. #386 When replacing a fuse with one of a ampere higher rating than the original, which of the following is true?
  86. #387 In order to definitively determine whether or not fuse "2", shown in the illustration is blown using an on-line testing technique, across what points... illustration
  87. #388 If a digital multimeter is set up as shown in figure "A" of the illustration, what would be displayed on the screen if the fuse being tested is not bl... illustration
  88. #389 When testing for blown fuses in a three-phase supply circuit to a motor, what would be an acceptable method?
  89. #390 To test fuses in an energized circuit, what testing apparatus or meter should be used?
  90. #391 What would cause a fuse to blow?
  91. #392 In figure "A" of the illustration, what is the position of the circuit breaker? Illustration EL-0033 illustration
  92. #393 What is the resistance reading at "2" on the megger scale shown in figure "A" of the illustration? Illustration EL-0044 illustration
  93. #394 As shown in the illustrated plots of uncorrected and temperature corrected insulation resistance readings for a particular piece of equipment, at what... illustration
  94. #395 When a fluorescent lamp fails to light and both ends of the tube are severely darkened, what must usually be replaced?
  95. #396 What is indicated by gradual blackening at the ends of component "4" shown in figures "B" and "C" of the illustration? Illustration EL-0081 illustration
  96. #397 During start-up of the circuit shown in figure "B" of the illustration, it is noted that the ends of component "4" alternately glow and become dark wi... illustration
  97. #398 In the lighting distribution circuit shown in the illustrated lighting panel L110 of the illustration, if all circuit breakers are closed and due to a... illustration
  98. #399 When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately. If not, what condition could the resultant flashing...
  99. #400 As shown in the illustration of a vessels navigational lighting circuit, if port running light "1" burns out, the trouble buzzer will sound and the po... illustration
  100. #401 As shown in the wiring diagram of the semi-automatic navigation lighting panel circuit, what would cause the buzzer to sound and for the indicator lig... 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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