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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 201–300 of 1,595 · page 3 of 16

  1. #201 What should be the primary consideration when choosing a battery for a particular application?
  2. #202 The individual 6 volt lead-acid batteries, when connected as shown in the illustration, as a battery bank would produce how many volts? Illustration E... illustration
  3. #203 The wet-cell storage batteries shown in the illustration are connected in what configuration? Illustration EL-0070 illustration
  4. #204 The nominal open-circuit voltage of one cell of a fully charged lead-acid battery is approximately how many volts?
  5. #205 How many cells are within in a 24 volt lead-acid battery?
  6. #206 In the illustrated views of a lead acid battery as shown in figures "A" and "B", what battery component has the sole function of preventing the indivi... illustration
  7. #207 The electrolyte used in a nickel-cadmium battery is distilled water and what other substance?
  8. #208 In general, why are nickel-cadmium storage batteries superior to lead-acid batteries?
  9. #209 What is the approximate voltage per cell produced by the nickel-iron (Edison) battery?
  10. #210 What is a hydrometer used to measure?
  11. #211 Why should a breakable, mercury-filled thermometer NOT be used in a lead-acid battery to measure electrolyte temperature?
  12. #212 Under normal conditions, storage batteries used for starting the emergency diesel generator are maintained in a charged state by which of the followin...
  13. #213 Which of the following statements concerning the specific gravity of a battery electrolyte is true?
  14. #214 Why should battery rooms be well ventilated during the charging process?
  15. #215 When a battery is continuously exposed to low temperatures, what is the best procedure to keep it from freezing?
  16. #216 When a hydrometer indicates specific gravity what is being compared?
  17. #217 What practice would be considered proper storage battery maintenance?
  18. #218 When charging, which of the following represents the recommended maximum allowable temperature for electrolyte in a lead-acid battery?
  19. #219 When charging lead-acid batteries, why should you reduce the charging rate as the battery nears its full charge capacity?
  20. #220 What will the charging of lead-acid storage batteries always result in?
  21. #221 What is the proper way to mix the electrolyte for a lead-acid battery?
  22. #222 When charging a 100 amp-hour lead-acid battery, what statement is true?
  23. #223 What should be done when correcting specific gravity readings of a lead-acid battery for existing temperature conditions?
  24. #224 What is the most reliable indication of the state of charge of a lead-acid battery?
  25. #225 What statement is true concerning the specific gravity of the electrolyte solution in a lead acid battery?
  26. #226 Which of the following statements concerning nickel-cadmium batteries is true?
  27. #227 When a nickel-cadmium battery begins gassing while connected to the battery charging circuit, what should be done?
  28. #228 What would you use to determine the state of charge of a nickel-cadmium battery?
  29. #229 Which statement is true concerning the charging a wet cell nickel-cadmium battery?
  30. #230 What could cause a very slow, but continual loss of electrolyte level from the cells of a storage battery?
  31. #231 What would cause a lead-acid battery to become hotter than normal during charging?
  32. #232 When troubleshooting a lead-acid storage battery, what is the best method for detecting a weak or dead cell?
  33. #233 In terms of the battery electrolyte, when performing maintenance of alkaline batteries what should be done?
  34. #234 When troubleshooting an alkaline storage battery, what is the best way to locate a weak or dead cell?
  35. #235 Which of the following losses is minimized by laminating the core of a DC generator armature?
  36. #236 What is the correct name for a variable resistor wired in series with the shunt field for the purposes of manually controlling generator output voltag...
  37. #237 As a DC armature revolves within a stationary magnetic field, the reversals of magnetization of the armature core lags the current reversals which pro...
  38. #238 In a shunt-wound DC generator, with what generator component are the shunt field windings connected in parallel with?
  39. #239 A variable shunt, connected across the series field coils of a DC compound wound generator, permits adjustment of the degree of compounding. What is t...
  40. #240 Which of the following components are used to convert alternating current produced in the DC generator armature windings to direct current?
  41. #241 What is the primary purpose of the brushes of DC generators?
  42. #242 Why are modern DC generators fitted with commutating poles?
  43. #243 Why are armature cores in a DC generator made of laminated steel sheets?
  44. #244 Which of the diagrams shown in the illustration depicts the proper method of aligning brushes on a commutator for a DC machine? Illustration EL-0057 illustration
  45. #245 Which of the following statements is true concerning the following illustration? Illustration EL-0028 illustration
  46. #246 As shown in the illustrated DC machine which is configured as a generator, what type of machine is illustrated in terms of the configuration of the wi... illustration
  47. #247 As shown in the illustration, which brush holder is of the reaction type? Illustration EL-0029 illustration
  48. #248 By what means is DC generator output voltage decreased?
  49. #249 Which of the terms listed best describes a compound-wound DC generator having a higher voltage at no load than at full load?
  50. #250 Prior to closing the circuit breaker when paralleling two DC generators, what must you be certain of?
  51. #251 By what means is an AC generator prevented from becoming motorized?
  52. #252 When two generators are on the line and are both connected across a shared load, how are they said to be operating?
  53. #253 What function does an equalizing connection between two compound-wound DC generators operating in parallel serve?
  54. #254 To effectively clean a commutator in good physical condition, what should be used?
  55. #255 How may propulsion DC motor brush pressures be calculated?
  56. #256 Brushes in a DC generator must be positioned in the neutral plane to avoid excessive sparking associated with the brushes. What device is used to prev...
  57. #257 What can cause uneven wear of the commutator surface on a direct current generator?
  58. #258 Hysteresis is one cause of electrical power loss associated with electricity generation equipment. What phenomenon results in hysteresis?
  59. #259 What may cause brush sparking in a DC generator during commutation?
  60. #260 The counter EMF of a DC motor is maximum when the __________.
  61. #261 In terms of voltage potential and current sources, how are shunt wound, series wound, and compound wound DC motors designed to operate?
  62. #262 If overloading an electric motor becomes necessary in an emergency situation, what should be done to prevent damage to the motor while allowing sustai...
  63. #263 What is the name of the DC motor speed control method utilized as shown in figure "B" of the illustration? Illustration EL-0101 illustration
  64. #264 In D.C. motor construction, where are the commutating windings wound?
  65. #265 What is the function of the commutator associated with a DC motor?
  66. #266 What is the characteristic of the mica used in the commutators of DC machinery?
  67. #267 In D.C. motor construction, with regard to the individual armature coils' ends, which statement is true?
  68. #268 What is the item referred to as a pigtail on a DC motor brush rigging?
  69. #269 What is the function of the interpoles installed in DC motors?
  70. #270 Which of the following types of DC motors is considered to produce the highest starting torque?
  71. #271 In a series wound motor, the current passing through the field windings also passes through what component?
  72. #272 How is the speed of a series wound winch motor controlled?
  73. #273 What type of DC motor is never connected to a belt driven load?
  74. #274 As load is added to a DC shunt motor, how will the motor respond?
  75. #275 Which of the following types of DC motors has its field connected in parallel with its armature?
  76. #276 In a short-shunt cumulatively compound-wound DC motor, how is the shunt field connected?
  77. #277 If an unloaded DC compound motor's shunt field were weakened by excessive rheostat resistance or by an open circuit, how would the motor respond?
  78. #278 What is the recommended method used to resurface an eccentric DC motor commutator?
  79. #279 In general, what can cause D.C. propulsion motor brush sparking to be excessive?
  80. #280 What should be included in performing proper maintenance of a D.C. motor's commutator?
  81. #281 Which of the listed faults can only be eliminated by turning or grinding the face of a commutator with a rigidly supported tool?
  82. #282 For routine cleaning of a commutator, what should be applied?
  83. #283 What is an important factor in minimizing D.C. motor commutator wear?
  84. #284 In addition to improper brush pressure or seating, what can result in excessive sparking at the brushes of a DC propulsion motor?
  85. #285 How can a shorted armature coil in a DC motor be detected?
  86. #286 Which of the listed conditions could cause a recently overhauled DC motor to have excessively hot windings and sparking at the brushes?
  87. #287 An open in the armature of a DC motor is suspected, but is not found by visual inspection of the commutator. What would be the next step in troublesho...
  88. #288 If a DC motor runs faster than designed, with all other conditions being normal, what could be the possible cause?
  89. #289 Besides for checking for circuit continuity, what can an ohmmeter be used for in diagnosing a DC motor?
  90. #290 One method of testing for a reversed shunt field coil in a DC motor is by connecting the coil to a low voltage source, and testing for polarity. How i...
  91. #291 How may temporary repairs to an open DC propulsion armature coil be made, allowing continued operation until permanent repairs can be made?
  92. #292 What would excessive sparking at the brushes of a running DC motor be an indication of?
  93. #293 Besides a condition of overload, what could be a cause of an open armature connection in a DC propulsion motor?
  94. #294 Which figure represents the schematic symbol shown in figure "2"? Illustration EL-0034 illustration
  95. #295 As shown in figure "6" of the illustration, what does the symbol represent as used in electrical drawings? Illustration EL-0026 illustration
  96. #296 What does the symbol labeled "OL" represent as shown in the power circuit on lines T1 and T3 to the motor as shown in figure "A" of the illustration?... illustration
  97. #297 Which of the electronic schematic symbols represents the capacitor illustrated in figure 2 of the illustration? Illustration EL-0015 illustration
  98. #298 Which of the listed figures in the illustration represents a transformer configured for single voltage primary and a tapped secondary? Illustration EL... illustration
  99. #299 Which of the illustrated resistors represents the schematic symbol shown in figure "C"? Illustration EL-0021 illustration
  100. #300 What is the shape of the schematic symbol for an operational amplifier used in an analog circuit?

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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About the Engine question pool

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.