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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 1,201–1,300 of 1,595 · page 13 of 16

  1. #1202 By what means should motor controller contacts be routinely cleaned?
  2. #1203 What item (or items) constitute routine AC motor controller maintenance?
  3. #1204 Before working on an electric cargo winch master switch or controller, what should be done?
  4. #1205 What damage may occur to the components of a winch master control switch, if the cover gasket becomes deteriorated?
  5. #1206 Using the illustrated catalog number selection chart, determine the correct catalog number for a motor starter that meets the following selection crit... illustration
  6. #1207 As shown in the illustration, what is the purpose of the Time Delay (TR) coil in the circuit? EL-0104 illustration
  7. #1208 If the contacts of a motor starter or controller fail to drop out when the 'stop' button is depressed, what could be the cause?
  8. #1209 What may cause magnetic controller contacts to become welded together during operation?
  9. #1210 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
  10. #1211 As shown in the illustration, what mechanism will disconnect the motor from the line in case of a sustained motor overload? EL-0080 illustration
  11. #1212 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? EL-0007 illustration
  12. #1213 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
  13. #1214 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
  14. #1215 As shown in figure "A" of the illustration, what is the primary reason that the propulsion transformers are configured differently so as to produce a... illustration
  15. #1216 Power conversion for use in DC propulsion drive motors is accomplished by what type of converter?
  16. #1217 The conversion of constant frequency power into adjustable frequency power in a modern AC propulsion drive system is commonly achieved through the use...
  17. #1218 A shown in figure "A" of the illustrated propulsion motor variable speed drive, what statement is true? EL-0140 illustration
  18. #1219 What type of electric propulsion system converter is shown in the illustration? EL-0155 illustration
  19. #1220 As shown the illustration of a cycloconverter for an AC synchronous propulsion motor, what statement is true concerning the operating motor frequency?... illustration
  20. #1221 Which of the following statements is true concerning a large polyphase synchronous main propulsion motor as used in an electric propulsion drive syste...
  21. #1222 Which of the following is a disadvantage of electric drive propulsion systems?
  22. #1223 What statement is TRUE concerning the Azipod propulsion system?
  23. #1224 Which of the following statement is TRUE concerning Azipod propulsion systems?
  24. #1225 As shown in figure "B" of the illustration, what statement is true concerning "regenerating" operation? EL-0162 illustration
  25. #1226 How is the main shaft rotation on an AC diesel-electric propulsion vessel normally reversed?
  26. #1227 How is the direction of propeller shaft rotation changed when directly coupled to an AC synchronous motor when driven by a variable frequency alternat...
  27. #1228 How is the direction of rotation of the main propulsion motor in a modern AC propulsion drive system reversed?
  28. #1229 How is the speed of the propeller shaft directly coupled to an AC synchronous propulsion motor changed when powered by a variable frequency alternator...
  29. #1230 What statement is TRUE concerning the speed of a synchronous ac propulsion motor?
  30. #1231 By what common means is the speed of the AC propulsion motor on a diesel- electric propulsion ship controlled?
  31. #1232 A shown in figure "A" of the illustrated propulsion motor variable speed drive, what statement is true? EL-0140 illustration
  32. #1233 How is the speed of the propeller shaft directly coupled to an AC synchronous drive motor changed when powered by either a dedicated or integrated con...
  33. #1234 A common method used to control the speed of a synchronous AC propulsion motor on a diesel-electric propulsion drive is by what means?
  34. #1235 As shown in the illustrated electric propulsion control scheme for a twin screw vessel, when the two shaft speeds are within 5% of each other, the bri... illustration
  35. #1236 Which of the listed temperature measuring devices installed on a large turbo-electric alternating current propulsion generator would be the most relia...
  36. #1237 Which of the listed devices is most likely to be installed on a large modern diesel- electric alternating current propulsion generator for commercial...
  37. #1238 Propulsion AC generators creating 4160 VAC use transformers to provide nominally 120 VAC to the automatic voltage regulator. What is the turns ratio o...
  38. #1239 An electric propulsion drive system in which the propulsion generator supplies power to both the propulsion motor and ship service loads is referred t...
  39. #1240 An electric propulsion drive system in which the propulsion generator only supplies power to the propulsion motor is referred to as what type of syste...
  40. #1241 In addition to improper brush pressure or seating, what can result in excessive sparking at the brushes of a DC propulsion motor?
  41. #1242 Which of the listed temperature measuring devices installed on a large turbo-electric alternating current propulsion generator would be the most relia...
  42. #1243 While standing an "at sea watch" onboard a modern rectified DC diesel-electric drive ship you notice the transformer core temperature slowly rising. W...
  43. #1244 While standing an "at sea watch" onboard an AC diesel-electric drive ship with a synchronous propulsion motor, you notice that the kwatt load is at ro...
  44. #1245 On a vessel with turbo-electric drive, which of the following conditions would indicate that the propulsion motor had dropped out of synchronization w...
  45. #1246 What equipment for modern SCR rectified DC propulsion drive systems is usually included in the package?
  46. #1247 Power conversion for use in DC propulsion drive motors is accomplished by what type of converter?
  47. #1248 As shown in the illustration of a DC diesel-electric propulsion drive system, what would be the set-up contactor configurations if #1 M/E is to be sec... illustration
  48. #1249 How are fuses usually rated?
  49. #1250 Due to the operating characteristics of the system, time lag fuses (or dual-element fuses) are necessary for use in what types of circuits?
  50. #1251 What is the characteristic that is associated with an "instantaneous-trip" single- element type fuse?
  51. #1252 Fuses are sometimes placed in series with a thermal trip-type circuit breaker. What is the purpose of a fuse used in this arrangement?
  52. #1253 In a dual element time-delay cartridge-type fuse, what type of protection is provided for motor applications?
  53. #1254 A fuse is the most common type of protection against a short-circuit fault in LV distribution circuits, motor circuits and for portable appliances. Wh...
  54. #1255 By what means does a molded-case breaker provide protection against short circuits?
  55. #1256 As shown in figures "E" and "F" of the pictured high voltage rack mounted circuit breaker, which figure represents the circuit breaker position when i... illustration
  56. #1257 When the operating handle of a molded-case circuit breaker is in the mid-position, what does this indicate?
  57. #1258 As shown in the illustration, which of the following pieces of equipment is supplied with a circuit breaker providing both overload and short-circuit... illustration
  58. #1259 What is a bus disconnect link used to isolate?
  59. #1260 What is meant by the term 'dielectric'?
  60. #1261 What is the greatest single cause of electrical failures?
  61. #1262 What is a common type of protective covering used on electrical conductors?
  62. #1263 Which of the listed types of lighting fixtures does the diagram shown in figure "A" of the illustration represent? EL-0081 illustration
  63. #1264 What type of circuit is represented by the diagram shown in the illustration? EL-0058 illustration
  64. #1265 As shown in the illustration, the change-over switch is what type of device? EL-0058 illustration
  65. #1266 As shown in the illustration, what event would give the same indication that would occur when a stern light circuit fuse blows open? EL-0058 illustration
  66. #1267 What is the purpose of the capacitor within component "5" of the circuit shown in figure "B" of the illustration? EL-0081 illustration
  67. #1268 A shown in the illustration, which of the lighting fixtures represents an incandescent bulb? EL-0122 illustration
  68. #1269 What are the operating characteristics of a step-down potential transformer in terms of the secondary load?
  69. #1270 Which of the listed transformers uses a single winding to produce voltage transformation?
  70. #1271 What is the function of the autotransformers used with autotransformer starters used on some large AC motors?
  71. #1272 How are power transformers rated?
  72. #1273 Why are transformer cores laminated?
  73. #1274 What is the purpose of the device labeled 'Man-Auto Sw.' in the illustrated switchboard? EL-0003 illustration
  74. #1275 Which of the listed sections of an emergency switchboard is used to supply power for alarm signals under emergency conditions?
  75. #1276 The timer element of a reverse power relay cannot be energized unless what condition is met?
  76. #1277 When electrical cables penetrate watertight bulkheads, what must be provided for?
  77. #1278 What is the reason that some electric cables are formed of stranded wire?
  78. #1279 Which of the following characteristics is most critical in determining the wire gauge size of the cable to be used in a particular circuit?
  79. #1280 As shown in the illustration, which of the following pieces of equipment is fed with the three conductor cable with the individual conductors having t... illustration
  80. #1281 How are the line losses in a distribution circuit kept to a minimum?
  81. #1282 Why is it necessary to perform periodic testing of correctly rated and properly installed circuit breakers?
  82. #1283 What should be done when performing maintenance of circuit breaker contacts?
  83. #1284 Which of the listed classes of electrical insulation is suited for the highest operating temperature?
  84. #1285 Which of the following procedures should be used to maintain a large electric motor during periods of inactivity?
  85. #1286 To check the three line fuses protecting a three-phase motor using a multimeter set up as a voltmeter, what should be done FIRST?
  86. #1287 As a general rule, what is the first troubleshooting action to be taken in checking inoperative electric circuits?
  87. #1288 In order to definitively determine whether or not fuse "1", shown in the illustration is blown using an on-line testing technique, across what points... illustration
  88. #1289 To test fuses in an energized circuit, what testing apparatus or meter should be used?
  89. #1290 In addition to short circuits and sustained overloads, in what other situation are fuses likely to blow?
  90. #1291 When replacing a fuse with one of a ampere higher rating than the original, which of the following is true?
  91. #1292 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 blown?... illustration
  92. #1293 If a circuit breaker that utilizes built-in, current limiting fuses (CLF's), cannot be closed or reset, what may be the problem? I. A blown current li...
  93. #1294 The ground indicating light on the main electrical switchboard is indicating a ground. What is the best procedure for locating the grounded circuit?
  94. #1295 Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out?
  95. #1296 In the illustration what is the component labeled "C"? EL-0033 illustration
  96. #1297 Which of the following expresses the relationship of the AC input frequency and DC ripple output frequency in a full wave rectifier?
  97. #1298 What does section "C" of the circuit shown in the illustration function as? EL-0085 illustration
  98. #1299 The transistors in figure "B" the illustrated circuit are connected using what type of coupling? EL-0048 illustration
  99. #1300 In figure "A" of the illustration, the battery Vbb and resistor Rb are in the circuit for what purpose? EL-0022 illustration
  100. #1301 In figure "A" of the illustrated circuit, the amplifier is connected in what basic configuration? EL-0045 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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