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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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All Electricity questions

Questions 401–500 of 1,595 · page 5 of 16

  1. #402 If all of the ground detection lamps burn with equal brilliance, whether the test button is depressed or released, what does this indicate?
  2. #403 A switchboard ammeter indicates a reading slightly above 'zero' when the leads are disconnected. What is this caused by?
  3. #404 In a three-phase electrical system, three ground detecting lamps are provided. One lamp goes dark and the others increase in brightness when the "grou...
  4. #405 A three-phase electrical system is equipped with ground detecting lamps. If one of the lamps is dark, and remains dark when the test switch is operate...
  5. #406 In an ungrounded distribution system, as compared to a normal indication, what is the indication on a switchboard of a current carrying conductor maki...
  6. #407 An open primary coil in a simple potential transformer will be indicated by which of the listed conditions?
  7. #408 If the illustrated device in figure "B" has a step-up ratio of 10 to 1 what voltage would be measured at the secondary shortly after the primary of th... illustration
  8. #409 What would be the source current and transformer current as shown in figure "B" of the illustration, with the secondary tap connected as shown, if the... illustration
  9. #410 In electronic circuitry, what does the abbreviation 'PCB' commonly represent?
  10. #411 Which line in figure "B" shown in the illustration represents the trailing edge of the wave? Illustration EL-0088 illustration
  11. #412 In comparing a semiconductor diode to a vacuum tube diode, what statement is true?
  12. #413 The multiplier prefix 'giga' (G) such as used in "gigabytes" represents what multiplication factor?
  13. #414 Which of the wave shapes shown in the illustration is termed a ramp or saw tooth wave? Illustration EL-0088 illustration
  14. #415 To minimize magnetic field interaction between electrical conductors in physical proximity, what is the best practice?
  15. #416 Which of the following statements represents an application of a silicon controlled rectifier?
  16. #417 Capacitors are commonly used on DC power supply circuits for engine room automation consoles. For what functional purpose are they primarily used in t...
  17. #418 All of the schematic diagrams shown in the illustration represent which of the listed solid-state circuits? Illustration EL-0069 illustration
  18. #419 In the regulated DC power supply illustrated, what is the function of section"B"? Illustration EL-0085 illustration
  19. #420 What is the function of section "D" of the circuit shown in the illustration? Illustration EL-0085 illustration
  20. #421 Given the circuit and individual AC and DC voltage waveforms shown in figure "A" producing the composite voltage waveform shown in figure "B", what wo... illustration
  21. #422 What is the correct name for the device used in an electrical circuit to change alternating current to direct current?
  22. #423 What is the direction of electron current through the load resistor in the circuit shown in the illustration? Illustration EL-0085 illustration
  23. #424 What does the drawing in the illustrated circuit represent? Illustration EL-0063 illustration
  24. #425 Which section of the circuit shown in the illustration smoothes out highest degree of pulsations? Illustration EL-0085 illustration
  25. #426 The characteristics of the device shown in figure "8" of the illustration includes a stable voltage and low current while operating. Because of this,... illustration
  26. #427 What is the name of the component labeled Q1 as shown in section "D" of the regulated DC power supply illustrated? Illustration EL-0085 illustration
  27. #428 What is the name of the semiconductor that decreases in resistance with an increase in temperature?
  28. #429 Which of the pictured solid-state semiconductor devices in the illustration is a rectifier bridge? Illustration EL-0068 illustration
  29. #430 A triac thyristor functions as a control device and can be thought of to function similarly as which of the following circuits?
  30. #431 Basically, a magnetic amplifier is a saturable-core reactor with the addition of what additional feature?
  31. #432 When a solid-state component of an electronic circuit is mounted to a metallic mass, what is the general purpose of that mass?
  32. #433 What will happen to a carbon resistor operating in electrical equipment that is NOT properly cooled?
  33. #434 How can the nominal resistance value of a typical carbon resistor in a circuit best be determined?
  34. #435 Although saturable reactors are extremely useful in some applications, why is their gain low?
  35. #436 Before touching a small capacitor connected to a de-energized circuit, or even one that is completely disconnected, you should do what FIRST?
  36. #437 Which of the following statements represents the important factor that must be considered when replacing a faulty diode in a generators excitation fie...
  37. #438 Two contributors of electronic console failures are heat and vibration. To combat some of their effects, what should be included in performing prevent...
  38. #439 If a delicate component must be soldered into a circuit, how can the component be protected from the heat of the soldering process?
  39. #440 Which type of flux should be used when soldering electrical wire connections for electronic components on printed circuit boards?
  40. #441 What should be done with a capacitor that is obviously discolored due to excessive heat?
  41. #442 If a digital multimeter is set up as shown in figures "A" and "B" of the illustration, what is the status of the silicon diode if the display reads OL... illustration
  42. #443 If a digital multimeter is set up as shown in figure "B" of the illustration to test a capacitor, what would the display read if the capacitor was fun... illustration
  43. #444 What is the name of the device shown in figure "2" of the illustration? Illustration EL-0068 illustration
  44. #445 If a digital multimeter is set up as shown in figures "A" and "B" to test a silicon diode, what is the status of the diode if the screen displays OL V... illustration
  45. #446 If a digital multimeter is set up as shown in figure "A" of the illustration to test a capacitor, what would the display read if the capacitor is shor... illustration
  46. #447 A capacitor is to be tested with a digital multimeter set up to measure ohms. If the meter is connected to a shorted capacitor, how would the meter di...
  47. #448 When troubleshooting electronic equipment, why should you use a high impedance multimeter?
  48. #449 Which of the following conditions would most likely lead to the failure of a resistor due to overheating?
  49. #450 What would be the indication of a burned-out LED?
  50. #451 Which of the following would best describe a standard electric meter movement that uses the principles of electromagnetism to measure current?
  51. #452 To limit the current flow through a DC voltmeter to as low a value as possible, what is the moving coil circuit provided with?
  52. #453 An internal resistance is placed in series with the meter movement of which of the following instruments?
  53. #454 Which of the listed meters uses a shunt connected in series with the load, but parallel with the meter movement?
  54. #455 Why are external shunts sometimes used with ammeters?
  55. #456 When a resistor is used as a shunt and is connected in parallel with a meter movement coil, what capability does this provide?
  56. #457 What is the instrument called a galvanometer used to measure?
  57. #458 What is an ammeter used to measure?
  58. #459 The clamp-on AC ammeter consists essentially of a split-core and a rectifier-type instrument connected to the secondary winding of a particular type o...
  59. #460 In order to take a current reading with a 'clamp-on' ammeter, what should be the status of the jaws of the instrument?
  60. #461 A digital multimeter, set up as a milliammeter on the 100 milliamp scale, is known to have an accuracy of plus or minus 2%. A meter reading of 5.0 mil...
  61. #462 A digital multimeter is set up as an ohmmeter on the 1 kohm scale. What does a display reading of 'OL' ohms as read across the ends of a wire conducto...
  62. #463 What practice could potentially damage a multimeter?
  63. #464 Whether analog or digital, what are most AC voltmeters calibrated to measure?
  64. #465 Which of the listed statements is correct when using an digital multimeter set up as an ohmmeter?
  65. #466 Which of the following conditions indicates a short circuited capacitor when checking its condition with a digital multimeter set up as an ohmmeter?
  66. #467 Before measuring an unknown resistance with an analog multimeter set up as an ohmmeter, what should you do?
  67. #468 As shown in figure "A" of the illustrated digital multimeter screen, what would be the significance of the symbol indicated by "2" being illuminated?... illustration
  68. #469 What is an ohmmeter used to measure?
  69. #470 As shown in figures "B" and "C" of the illustration, what should be the switch position and which test lead terminal jacks should be used if your inte... illustration
  70. #471 Circuit resistance is usually measured off-line (de-energized) with an ohmmeter. In the absence of an ohmmeter, however, resistance may be INDIRECTLY...
  71. #472 If the pointer fails to return to zero when a hand-cranked megger is disconnected, what does this indicate?
  72. #473 Under what circumstance would a hand-held portable phase sequence indicator be used should the main switchboard mounted fixed phase sequence indicator...
  73. #474 As shown in the illustrated devices and symbols, which of the devices represents an open general purpose relay? Illustration EL-0005 illustration
  74. #475 Which of the following illustrated manual motor starters represents the wiring diagram illustrated in figure "A"? Illustration EL-0023 illustration
  75. #476 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?
  76. #477 Which of the following statements represents the main difference between a relay and a contactor?
  77. #478 Which of the motors for the devices listed below is fitted with an instantaneous overload relay?
  78. #479 An across-the-line starter is typically used for which of the following applications?
  79. #480 What is the functional name of an electrical device which prevents simultaneous energization of loads thereby preventing damage or injury.
  80. #481 What functionality does a low-voltage protection circuit as used in electric motor starting equipment provide?
  81. #482 Which of the listed items will stop a motor due to a reduction in voltage and automatically restart it when the voltage is restored to normal?
  82. #483 In the illustrated motor controller, what do the contacts across terminals "3" and "4" of the control circuit represent? Illustration EL-0017 illustration
  83. #484 As shown in the illustration, which of the following conditions will occur as a result of a momentary loss of power? Illustration EL-0017 illustration
  84. #485 As shown in the illustration, what type of starter is illustrated? Illustration EL-0104 illustration
  85. #486 In the illustration shown, what would be the functional name for the coil represented as '1S'? Illustration EL-0012 illustration
  86. #487 As shown in the illustration, assuming power is available at the control circuit, which listed action will occur FIRST when the "off-run" switch is pl... illustration
  87. #488 Which of the following statements is true concerning the motor controller circuit shown in the illustration? Illustration EL-0004 illustration
  88. #489 In the illustration shown, what type of protection is provided the potable pump drive motor? Illustration EL-0043 illustration
  89. #490 A three-phase, induction-type motor experiences an open in one phase. Which of the listed automatic protective devices will prevent the motor from bei...
  90. #491 If the circuit shown in the illustration were energized and operating properly, which of the devices listed would be open? Illustration EL-0007 illustration
  91. #492 When a motor is started by the controller shown in figure "C" of the illustration, what circuit components are in the holding current flow path throug... illustration
  92. #493 As shown in the illustrated electrically operated watertight door controller, how is the rotation direction of the door motor reversed? Illustration E... illustration
  93. #494 By what means is the burning of controller contacts due to arcing, when opening, prevented?
  94. #495 When rolling over a DC main propulsion motor in local emergency mode or throttle bypass mode, what must be done with the variable rheostat in terms of...
  95. #496 Which of the following statements is true concerning the operation of modern marine electric drive DC propulsion motors?
  96. #497 As shown in figure "B" of the illustration, when the DC motor in figure "A" is operating at minimum speed what are the armature and field characterist... illustration
  97. #498 Before working on an electric cargo winch master switch or controller, what should be done?
  98. #499 Which of the following represents the accepted method of cleaning dust and foreign particles from electrical equipment while limiting damage to electr...
  99. #500 Moisture damage, as a result of condensation occurring inside of the cargo winch master switches, can be reduced by the use of what installed equipmen...
  100. #501 What damage may occur to the components of a winch master control switch, if the cover gasket becomes deteriorated?

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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