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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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Questions 101–200 of 1,595 · page 2 of 16

  1. #101 When would be the safest time to close the ship's main switchboard "shore power" circuit breaker?
  2. #102 How are the number of cycles per second developed by the alternator aboard your vessel determined?
  3. #103 The governor control switch of an alternator is moved to the 'raise' position. What will be the effect of this action?
  4. #104 How is the power factor of an AC generator operating singularly determined?
  5. #105 Prior to manually starting an AC generator prime mover and paralleling in the manual control mode, what should be the position of the voltage regulato...
  6. #106 How is the frequency of an alternator at a given RPM determined?
  7. #107 Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the...
  8. #108 What is the most practical way to control the voltage output of an AC generator?
  9. #109 How will the value of the output frequency change if the load is removed from a turbo generator having a governor speed droop setting of 3%?
  10. #110 When securing an AC generator, what should be your FIRST action in accomplishing the procedural steps?
  11. #111 Which of the methods listed below is used to provide the rotational torque to cause an AC generator to turn?
  12. #112 What devices maintains equal power factors on paralleled AC generators automatically?
  13. #113 Attempting to parallel an AC generator which is out of phase with the bus will result in which of the following conditions?
  14. #114 You are attempting to parallel two AC generators and the synchroscope pointer is revolving in the fast direction. What is the frequency of the oncomin...
  15. #115 Which of the following statements is true concerning the operation of two alternators in parallel?
  16. #116 When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. What does...
  17. #117 Two AC generators of the same capacity are operating in parallel. One with a zero speed droop setting and the other with a 5% speed droop. If its capa...
  18. #118 What device is used so that the kilowatt load sharing can be adjusted on paralleled generators?
  19. #119 If the excitation of an alternator operating in parallel is decreased below normal and the other above normal, what will be the result on the alternat...
  20. #120 You are paralleling two alternators. The synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position....
  21. #121 A main switchboard synchronizing panel is fitted with two synchronizing lamps and a synchroscope. When paralleling, if the synchroscope pointer is at...
  22. #122 When an alternator is to remain idle for even a few days, what should be done?
  23. #123 Which of the following materials is recommended for burnishing the slip rings of an alternator after grinding or turning?
  24. #124 How may chattering of the collector/slip ring brushes on a generator be remedied?
  25. #125 Which of the following statements, concerning the cleaning maintenance of a brushless generator, is correct?
  26. #126 In performing routine maintenance of a ship's service alternator, what should be included?
  27. #127 If rotor-to-stator air gap readings for an electrical generating machine have changed significantly from the last reading, what should be checked?
  28. #128 Rotor-to-stator air gap readings should be periodically taken for electrical generation equipment. What is the best tool to use to take these measurem...
  29. #129 With regard to the maintenance of electrical generating machines with insulated pedestal bearings, what practice should be avoided?
  30. #130 If a shipboard AC generator experiences a failure to produce a voltage, what may be the cause?
  31. #131 What may be the cause of an AC generator to fail to produce a voltage?
  32. #132 An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and making specific observations. Wha...
  33. #133 How can the loss of residual magnetism in an alternator or generator be corrected?
  34. #134 In actual applications, electrical connections associated with 'R1, R2 and R3' of the transmitter to 'R1, R2, and R3' of the indicators shown in figur... illustration
  35. #135 If coil 'R1-R2-R3' on the transmitter in figure "C" shown in the illustration is turned 30 degrees clockwise, how will the corresponding coils 'R1-R2-... illustration
  36. #136 As shown in figure "A" of the illustration, fine adjustments such as "rate of turn signal" have no effect on steering stand operation when the 'operat... illustration
  37. #137 What controls rudder movement when the Operation Selector Switch shown in figure "A" of the illustration is in the "Controller" position? Illustration... illustration
  38. #138 When power is restored after a complete power failure, how will the steering gear pump motor which was on-line respond?
  39. #139 What is the functional purpose of the 'LSH' contacts for the hoist controller circuit shown in the illustration? Illustration EL-0102 illustration
  40. #140 As shown in the illustration, what is the functional purpose of the normally closed and normally open auxiliary contacts of the hoist and lower contac... illustration
  41. #141 Which of the listed conditions occur when '4th point lower' is selected on the winch hoist controller shown in the illustration? Illustration EL-0102 illustration
  42. #142 What functionality do the 'MS 1' contacts of the master switch shown in the illustration provide? Illustration EL-0102 illustration
  43. #143 The progressive operation of the contactors marked "1A" through "4A" provide the winch hoist controller shown in the illustration with what functional... illustration
  44. #144 What is the function of the electric brake on an deck cargo winch?
  45. #145 In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by what means?
  46. #146 When the control handle is in the 'off' position, what is the status of the solenoid actuated brake of an electric winch?
  47. #147 What does the component labeled "B" shown in the illustration represent? Illustration EL-0093 illustration
  48. #148 As shown in the illustration, which of the following statements is correct concerning the circuits in a sound powered telephone system? Illustration E... illustration
  49. #149 The pushbutton on the handset of a ship's sound-powered telephone must be depressed in order to do what?
  50. #150 Where is the power necessary to energize the howler "relay" coil at the engine room station as shown in the illustration? Illustration EL-0093 illustration
  51. #151 Concerning the illustrated fire detection and alarm system, what statement is true concerning the wiring between zones? Illustration EL-0114 illustration
  52. #152 Impressed current cathodic hull protection systems are commonly used on modern vessels. What are these systems designed to replace or reduce?
  53. #153 For more complete vessel protection when using an impressed current cathodic system, what other features are built into the system?
  54. #154 As part of a routine maintenance program for deck machinery motor controllers, what should be done?
  55. #155 If deck machinery is expected to be idle for an extended period of time, what should be done?
  56. #156 As shown in figure "1" of the illustration, a correctly connected synchronous transmission causes the receiver to be in correspondence with the transm... illustration
  57. #157 As shown in the illustrated wiring diagram for an engine order telegraph system, what statement concerning the constant ringing and trouble alarm is t... illustration
  58. #158 Erratic operation of the device represented in the diagram labeled "A" shown in the illustration could be traced to what condition? Illustration EL-00... illustration
  59. #159 If it is required that the coils 'R1-R2-R3' in the indicator of figure "A", turn opposite to those in the transmitter, as shown in the illustration, w... illustration
  60. #160 Which of the following conditions will occur if the brake solenoid coil burns out on a cargo winch with an electrical brake?
  61. #161 The winch shown in the illustration will operate normally in all speeds in both directions, with the exception that it will not accelerate into 'fifth... illustration
  62. #162 As shown in the illustration, what is responsible for maintaining the "UV" relay energized when the master switch handle is moved away from the "off"... illustration
  63. #163 In the system shown in the illustration, the engine room station is unable to signal any other station, nor is any other station able to signal the en... illustration
  64. #164 In the circuit 'B' of the illustration, what would be the result of the upper heating element being burned out and open circuited? Illustration EL-004... illustration
  65. #165 What will be the resulting current when a voltage of 110 VDC is applied to a resistance of 32 ohms in figure "A" of the illustrated circuit when the s... illustration
  66. #166 If the voltage supplied to the lighting circuit is 110 volts, how much current is drawn by a 100 watt light bulb?
  67. #167 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?
  68. #168 What will be the resulting current when a voltage of 115 VDC is applied to a resistance of 12 ohms in figure "A" of the illustrated circuit with the s... illustration
  69. #169 What would be the total current flowing in the circuit shown in figure "B" of the illustration if the source is 30 volts, the resistance of R1 is 10 o... illustration
  70. #170 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...
  71. #171 What will be the resulting current when a voltage of 442.7 VDC is applied to a resistance of 1.25 ohms in figure "A" of the illustrated circuit when t... illustration
  72. #172 What is the current flow through R1 of the circuit in figure "B" of the illustration with the switch closed if the resistance of R1 is 2 ohms, R2 is 3... illustration
  73. #173 A lamp has a source voltage of 110 volts and a current of 0.9 amps. What is the hot resistance of the lamp filament?
  74. #174 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? Illustration... illustration
  75. #175 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
  76. #176 In figure of "A" of the illustrated circuit, what is the voltage measured across R1 if the battery voltage is 24 volts, the resistance of R1 is 34 ohm... illustration
  77. #177 As shown in figure "A" of the illustration if the applied voltage is 12 VDC, the resistance of R1 is 10 ohms, and R2 is 10 ohms what is the current fl... illustration
  78. #178 What is the voltage across 'R1' of figure "B" of the illustrated circuit with the switch closed if the applied voltage is 24 volts and resistance of R... illustration
  79. #179 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
  80. #180 What would be the terminal voltage and ampere-hour capacity of the battery bank if each battery was rated at 50 amp-hours and 6 volts? Illustration EL... illustration
  81. #181 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
  82. #182 A battery is connected to a circuit containing three resistors in parallel. The values of the three resistors are 2 ohms, 3 ohms, and 6 ohms. What is...
  83. #183 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
  84. #184 What is the power consumed by 'R2' in the circuit illustrated in figure "B", if the applied voltage is 24 volts and the resistance of R1 is 3 ohms, R2... illustration
  85. #185 How is the power dissipated as heat in a direct current circuit calculated?
  86. #186 What is the wattage of a heating element drawing a current of 30 amperes, at 120 volts?
  87. #187 A 125 volt DC motor is rated at 10 kW. What is the current rating of the motor?
  88. #188 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...
  89. #189 What power would be consumed by the series resistor in the circuit shown in the illustration if the source is 30 volts, the resistance for R1 is 10 oh... illustration
  90. #190 How many watts of power is equal to one horsepower?
  91. #191 A three-phase alternator operates at 450 volts with a 0.8 power factor. If the ammeter indicates 250 amperes, what should be the kW meter reading?
  92. #192 What will be the frequency of a three-phase, 16 pole, AC generator operating at 3000 revolutions per minute?
  93. #193 What is the rotor speed of a six pole, 60 cycle, induction motor operating at full load with 3% slip?
  94. #194 A four pole turbo generator is used in conjunction with a 160 pole propulsion motor. If the generator is turning at 3,200 RPM, what is the current spe...
  95. #195 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?
  96. #196 In a 60 Hz AC system, what is the duration in seconds for one complete cycle?
  97. #197 The turns ratio of the step down transformer with dual voltage secondary as shown in figure "B" of the illustration is two to one (total). If 440 volt... illustration
  98. #198 What is the maximum allowable primary current of a 2 kVA step-down transformer with a four to one turns ratio if the primary is connected across a 440...
  99. #199 In figure "2" of the diagram shown in the illustration, the three phase power transformer has a step-down turns ratio of four to one. If a three-phase... illustration
  100. #200 A load is connected across the secondary of the step up transformer shown in figure "B" of the illustration and the current drawn by the load is 10 am... 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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