Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR
USCG Marine Electrical Systems (Set 18)
30:00
|Question 1 of 30
Question Navigator
Correct Incorrect Pending Starred
Question 1 of 30
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? Illustration EL-0007
Browse Questions in Set 18
30 MCQs #1 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? Illustration EL-0007 #2 What can be the cause of excessive heat or burning contacts in an operating motor controller? #3 The illustrated motor fails to start and gives a loud hum when the start button is depressed, what should then be your first action? Illustration EL-0007 #4 In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 5 reads line voltage, while the voltmeter reading between 2 and 5 reads 0 VAC. What is most likely the problem? Illustration EL-0007 #5 If the motor shown in the illustration will not start when the "off-run" switch is placed in the run position, which of the listed components should be checked FIRST? Illustration EL-0017 #6 When troubleshooting a motor controller, all indications are that a relay coil should be energized. If there was no magnetic pull, with rated voltage measured across the coil, what would be the most probable cause? #7 When troubleshooting a magnetic controller, it is found that the contacts are welded together. What is the most probable cause? #8 As shown in figure "A" and "B" of the illustration, the potable water pump is short cycling by the action of the pressure switch as a result of an unusually high level in the potable water hydro pneumatic header tank. What is most likely the cause? Illustration EL-0043 #9 If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, what is the probable cause? #10 A loud buzzing noise coming from the contacts in a magnetic controller can be caused by what condition? #11 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 depressed and the following readings are taken, what is the problem? "X1" to "X2" reads 115 VAC; "1" to "X2" reads 115 VAC; "2" to "X2" reads 0 VAC; and "3" to "X2" reads 0 VAC. Illustration EL-0123 #12 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 open-circuited? Illustration EL-0214 #13 What can cause the pitting or welding of controller contacts? #14 If many turns of an alternating current coil for a contactor become short circuited, what will happen to the coil? #15 At a minimum threshold, how many milliamps of current through the body produces a painful sensation that most people would perceive as an electric shock? #16 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would be unable to let go of the energized electrical conductor due to involuntary muscular contraction? #17 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would experience respiratory paralysis and be unable to breathe while still in contact with the energized conductor? #18 At a minimum threshold, how many milliamps of current through the body produces a condition where most people would suffer ventricular fibrillation and could only be resuscitated with a ventricular defibrillator? #19 With all other factors considered equal (such as voltage, conducting path through the body and the duration of contact), contact with an energized electrical system conductor of which system type would produce the most damaging effect? #20 Before electrical work can be safely undertaken, the equipment must be de-energized, locked and tagged out, and verification must be made that the circuit is actually dead. What testing device is most certain to reliably verify that a circuit is actually dead? #21 Which of the following devices would be forbidden to use as a primary means of electrical isolation? #22 Which of the following voltage testers would be associated with high quality, be safe to use, and minimize the electric shock hazard? #23 What is the primary means by which an electrical maintenance worker is protected from electrical hazards while performing work on an electrical circuit? #24 After prior isolation and lockout/tagout procedures are performed, which electrical device requires discharging any stored electrical energy before any work may safely begin? #25 AC circuits can possess characteristics of resistance, inductance, and capacitance. In terms of units of measure, how is the capacitive reactance of the circuit expressed? #26 The root mean square (RMS) value of a sine-wave current may also be expressed as what value? #27 For the purpose of calculating apparent power, which of the following procedures should be used to determine the total load current of a three-phase, delta wound, AC generator? #28 If the voltage and the current developed in an AC circuit reach their peak values at the same time (with a phase angle difference of zero), what is the power factor considered to be? #29 An accidental path of low resistance bypassing the intended path and allowing passage of an abnormally high amount of current is known as what? #30 In the flow of one cycle of single phase alternating current past any given point in a circuit, how many times will the current peak to a maximum?
Question Discussion & Notes
0Have a doubt, memory trick, or exam update? Share your insights with fellow mariners.
Loading mariner discussions...