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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 701–800 of 1,595 · page 8 of 16

  1. #702 Why should battery rooms we well ventilated during the charging of storage batteries?
  2. #703 Which of the following procedures represents the best method to prevent the freezing of batteries continuously exposed to low temperatures?
  3. #704 Which of the following statements describes the effects of ambient temperature on local action within lead-acid storage batteries?
  4. #705 As shown in the cutaway view of the lead acid battery in figure "A" of the illustration, if one half of the battery's cells are revealed by the cutawa... illustration
  5. #706 What is the nominal open-circuit cell voltage of one lead-acid storage battery cell?
  6. #707 To keep emergency lead-acid batteries in a full state of charge for emergency use, what is normally done?
  7. #708 Assuming that the electrolyte has had sufficient time to be uniformly diffused throughout the cell, if the open-circuit cell voltage as measured by a...
  8. #709 The nominal voltage of one cell of a wet cell nickel-cadmium battery is approximately how many volts?
  9. #710 Why are nickel-cadmium batteries superior to lead-acid batteries for standby service?
  10. #711 What is the approximate discharge voltage produced by one cell of a wet type nickel- cadmium battery at 75% of charge?
  11. #712 What material are the plates of a wet cell NiCad storage battery made of?
  12. #713 What is the most reliable and preferred method for determining the state of charge of a wet-cell NiCad battery?
  13. #714 Which of the illustrated motors has an open motor enclosure? EL-0001 illustration
  14. #715 What will be the impact of reduced voltage applied to a motor during the starting period?
  15. #716 Which of the illustrated motors has an open, drip-proof (ODP) motor enclosure? EL-0001 illustration
  16. #717 What is he most practical method of controlling the RPM of a multi-speed AC motor operating at a constant frequency?
  17. #718 As shown in figure A" of the illustrated motor nameplate, how much current could the motor safely draw on a continuous basis at sea level without over... illustration
  18. #719 Regarding an induction motor, what does the power developed by the rotor automatically adjust itself to?
  19. #720 Which of the following motors has a frame configuration for solid base mounting only? EL-0184 illustration
  20. #721 Which type of AC single-phase motor will also operate on direct current?
  21. #722 What is the main function in the use of a capacitor for starting a single phase motor?
  22. #723 As shown in figures "A", "B", "C", and "D" of the illustration, what is the usual means by which the rotation direction of the motor is reversed? EL-0... illustration
  23. #724 What is the main purpose of the auxiliary winding on a split-phase, single-phase motor?
  24. #725 What type of rotor is most commonly used in the split-phase family of single-phase motors?
  25. #726 Which of the pictured motors within the split phase family of single phase induction motors represents a split phase, resistive start, induction run m... illustration
  26. #727 Within the split phase family of single phase motors, what are the operational characteristics of the motor shown in figure "A" of the illustration? E... illustration
  27. #728 Which statement is true concerning a split-phase induction motor?
  28. #729 A shaded-pole motor is a specific type of motor included in what class of motor?
  29. #730 What are the operational characteristics of the split phase motor shown in figure "A" of the illustration? EL-0215 illustration
  30. #731 Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency?
  31. #732 Assuming that the 3-phase power source has a phase sequence of A-B-C and that the motor is connected as shown in figure "A", if the motor has a clockw... illustration
  32. #733 How is the difference between the synchronous speed of a three phase induction motor and its operating speed correctly expressed?
  33. #734 The torque-speed and current-speed curves for a three-phase induction motor with a squirrel cage rotor are shown in figures "A" and "B" of the illustr... illustration
  34. #735 In a three-phase, squirrel-cage type, induction motor, how is the primary rotating magnetic field established?
  35. #736 As shown in the two-speed single winding three phase motor connection diagrams illustrated in figure "B", what is the connection scheme associated wit... illustration
  36. #737 What is the characteristic of a wound-rotor induction motor, with a high resistance inserted in series with the rotor winding at startup?
  37. #738 As shown in the illustrated wound-rotor induction motor, what statement is true concerning motor lead connections? Illustration EL-0148 illustration
  38. #739 What type of AC motor would use a rheostat in the rotor circuit to vary the speed of the motor?
  39. #740 A degree of control over the speed of a slip ring induction motor can be obtained by what means?
  40. #741 Which of the following physical characteristics does a three-phase wound-rotor induction motor possess that a squirrel cage induction motor does not?
  41. #742 By what means is a synchronous motor started and brought nearly to synchronous speed?
  42. #743 Concerning the operating characteristics of a synchronous motor, what statement is true?
  43. #744 Assuming that a three phase synchronous motor is separately excited, what statement is true concerning power supplies?
  44. #745 Occasionally a synchronous motor is configured without an external shaft to drive a load. In this case, the sole purpose of the synchronous motor is i...
  45. #746 Not only can a synchronous motor drive a load with greater efficiency than an induction motor, a fringe benefit of the synchronous motor is the abilit...
  46. #747 In terms of voltage potential and current sources, how are shunt wound, series wound, and compound wound DC motors designed to operate?
  47. #748 How can the direction of rotation of a DC motor be reversed?
  48. #749 What is the name of the DC motor speed control method utilized as shown in figure "B" of the illustration? EL-0101 illustration
  49. #750 From the instant of start-up, through the acceleration period, and until the motor reaches rated speed, when is the counter EMF produced in the windin...
  50. #751 Which of the following statements describes what will happen when both the polarity of the field poles, and the direction of current to the brushes of...
  51. #752 As shown in figure "B" of the illustration, what does the M-G set's three-phase drive motor mechanically drive? EL-0101 illustration
  52. #753 If a DC motor has its armature and field connected across a resistor when the motor is disconnected from its power supply, what statement is true?
  53. #754 What is an advantage of DC motors over AC motors?
  54. #755 The torque produced by a DC motor armature is the multiplication product of two factors, one being the density of the magnetic flux which is dependent...
  55. #756 As shown in the illustration, which brush holder would be appropriate to use in a bi- directional motor? EL-0029 illustration
  56. #757 As shown in the illustration, which brush holder is of the reaction type? EL-0029 illustration
  57. #758 Which of the following types of DC motors is considered to produce the highest starting torque?
  58. #759 In a series wound motor, the current passing through the field windings also passes through what component?
  59. #760 How is the speed of a series wound winch motor controlled?
  60. #761 What type of DC motor is never connected to a belt driven load?
  61. #762 What type of DC motor has extremely high starting torque, but has poor inherent speed regulation?
  62. #763 The wiring diagram found in figure "C" of the illustration represents what type of DC motor? EL-0054 illustration
  63. #764 What type of DC motor has relatively low starting torque, but has excellent inherent speed regulation?
  64. #765 In a shunt wound DC motor, how is the shunt field connected?
  65. #766 What are the characteristics of the field winding of a shunt wound motor?
  66. #767 The wiring diagram found in figure "A" of the illustration represents what type of DC motor? EL-0054 illustration
  67. #768 What statement is true concerning speed control of a shunt wound DC motor?
  68. #769 The wiring diagram found in figure "B" of the illustration represents what type of DC motor? EL-0054 illustration
  69. #770 Which of the listed DC compound motor connection schemes is the most commonly used?
  70. #771 When a compound wound DC motor is cumulatively compounded, what does this mean?
  71. #772 When a compound wound DC motor is differentially compounded, what does this mean?
  72. #773 Assuming that a cumulatively compounded DC motor is fitted with interpoles and compensating windings, normally how is the direction of rotation in suc...
  73. #774 What is the purpose of an electro-magnetic relay?
  74. #775 Which of the following statements represents the main difference between a relay and a contactor?
  75. #776 What is the functional name of an electrical device which prevents simultaneous energization of loads thereby preventing damage or injury?
  76. #777 Which of the following illustrated manual motor starters represents the wiring diagram illustrated in figure "A"? EL-0023 illustration
  77. #778 What is one function of the movable cams in a drum-type winch motor controller?
  78. #779 What is the name of the type of motor control circuit that will not permit automatic restarting after power is restored, following a power failure?
  79. #780 As shown in the illustration, by what means are all the 'MS' contacts are opened and closed? EL-0073 illustration
  80. #781 If a three-phase motor controlled by the control circuit illustrated in figure "B" of the illustration, is running in the forward direction, which of... illustration
  81. #782 With what kind of starting equipment are most three-phase induction motors of five horsepower or less started?
  82. #783 Concerning the illustrated motor controller circuit, where is the location of the motor "run" indicator light? EL-0004 illustration
  83. #784 Which of the following contactors or relays has a timing function for the transition from start to run? EL-0080 illustration
  84. #785 As shown in the illustration, what type of motor and motor starter are featured? EL-0136 illustration
  85. #786 As shown in the illustrated steering hydraulic pump motor controller, what statement is true? EL-0119 illustration
  86. #787 As shown in figure "A" of the illustration, what is the purpose of the "test button"? EL-0178 illustration
  87. #788 As shown in the illustrated feeder disconnect controller, what statement is true? EL-0138 illustration
  88. #789 Which of the following pictures represents a magnetic reversing or two-speed motor starter? EL-0179 illustration
  89. #790 Auto-transformer starters, sometimes called starting compensators, are sometimes used with larger polyphase induction motors. What function do they pe...
  90. #791 In general, what type of starter would be used to connect polyphase induction motors to full line voltage at the instant of start-up?
  91. #792 Assuming the ladder diagram of figure "1" and the corresponding input/output diagram of figure "2" represents a simple PLC motor controller, what stat... illustration
  92. #793 Concerning figure "A" of the illustration, if the illustrated PLC ladder diagram is for a simple motor controller, what does "Input A" represent? EL-0... illustration
  93. #794 In the illustrated solid-state "soft" starter for a three phase induction motor as shown in figure "A", what is the name of the devices that are contr... illustration
  94. #795 By what means is the burning of controller contacts due to arcing, when opening, prevented?
  95. #796 As shown in the illustration of an electrically operated watertight door controller, what type of motor is used to open and close the watertight door?... illustration
  96. #797 As shown in the illustration of an electrically operated watertight door controller, how is reversal of the direction of motor rotation achieved? EL-0... illustration
  97. #798 As shown in the illustration of an electrically operated watertight door controller, how is the motor stopped automatically when the door is wedged cl... illustration
  98. #799 As shown in the illustration of an electrically operated watertight door controller, how is the motor stopped automatically when the door is wedged op... illustration
  99. #800 Which of the following statements about a three-phase wye connected alternator is correct?
  100. #801 Of the listed factors that influence the amount of RMS voltage induced in the windings of an AC generator operating at a constant 60 Hz frequency, whi...

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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