Description : Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to ... D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.
Last Answer : Answer: C
Description : A circuit that has one of two wires in contact with the hull of a ship, is called a _____________. A. grounded circuit B. short circuit C. series circuit D. closed circuit
Last Answer : Answer: A
Description : When testing for blown fuses in a three-phase supply circuit to a motor, you should first ___________________. A. apply the megger across the tops of the line fuses B. apply an ammeter diagonally across ... of the line fuses D. ensure the circuit is de-energized, and then use a continuity tester
Last Answer : Answer: D
Description : Component 'C' in section 'I' shown in the illustration represent ____________. EL-0093 A. a selectable holding coil arrangement B. a 'fuse blown' indicator circuit C. 'reset' and 'trouble' lamps D. a handset with switch and voice elements
Description : Which of the following conditions is most likely to occur if a single element fuse were used to replace a blown dual element fuse in a motor controller circuit? A. The fuse will blow when the motor ... overheats at high motor loads. C. The motor runs at reduced voltage. D. The motor runs normally.
Description : In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 6 reads line voltage, while the voltmeter reading between 2 and 6 reads 0 VAC. The problem is __________. EL- ... in the 'M' coil, 'Ma' contact/start switch or overload contacts D. fuse '10a' is blown
Last Answer : Answer: B
Description : The ground indicating light on the main electrical switchboard is indicating a ground. The best procedure for locating the grounded circuit is to _____________. A. trace the circuit paths while looking for ... a time, until the lights no longer indicate a ground D. check all circuits for continuity
Description : An instantaneous-trip-type fuse will _____________. A. open as soon as the load current exceeds its set point B. allow a preset delay between overcurrent and melting C. open a circuit by using a time delay element with a magnetic trip D. reset itself when the overcurrent is corrected
Description : A circuit breaker and a fuse have a basic similarity in that they both _____________. A. can be reset to energize the circuit B. should open the circuit when overloaded C. will burn out when an over current flow develops D. all of the above
Description : When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown ... of the coil's leads to ground D. a higher-than-normal voltage reading across the winding
Description : For more complete vessel protection when using an impressed current cathodic system _____________. A. all ship's service alternators have additional temperature sensing devices and a thermal recorder ... with the hull and the propeller shaft is grounded through a slip ring/brush arrangement
Description : While testing a semi-conductor diode with an ohmmeter, both the forward and reverse readings are almost in the infinity range. This would indicate that the unit is _____________. A. good B. open C. grounded D. shorted
Description : If a circuit breaker that utilizes built-in, current limiting fuses (CLF's) cannot be closed, the problem may be traced to __________. A. a blown CLF plunger holding the trip bar in the open position B. a missing CLF C. a misaligned limiter housing assembly D. all of the above
Description : In addition to short circuits and sustained overloads, fuses are likely to blow due to _____________. A. loose fuse clips B. low ambient temperatures C. low contact resistance D. all of the above
Description : In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. This is accomplished by opening the _____________. A. reverse power relay B. bus disconnect link C. generator bus fuse connections D. power directional relay
Description : If an electric motor fails to start, you should FIRST check the _____________. A. phase sequence B. ampere load C. fuse or circuit breaker D. line frequency
Description : The part of a fuse that melts and opens the circuit is made of _____________. A. copper and antimony B. steel and babbitt C. aluminum or beryllium alloy D. zinc or an alloy of tin and lead
Description : A circuit breaker differs from a fuse in that a circuit breaker _____________. A. melts and must be replaced B. is enclosed in a tube of insulating material with metal ferrules at each end C. gives no visual indication of having opened the circuit D. trips to break the circuit and may be reset
Description : An accidental path of low resistance which passes an abnormal amount of current is known as a/an _____________. A. polarized ground B. short circuit C. ground reference point D. open circuit
Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents
Description : Which of the listed conditions might contribute to very rapid wearing of a DC machine's commutator bars? A. A grounded commutator bar B. Using improper carbon brushes C. Aligning the front and rear mica V-rings improperly D. An open circuit in the armature
Description : Why is it a poor practice to use a high wattage soldering iron when soldering or desoldering components on a printed circuit board? A. The circuit board will blister and warp. B. The foil wire bonded ... board has a low melting temperature. D. The solder is kept to a dull heat dissipating finish.
Description : Before touching a small capacitor connected to a de-energized circuit, or even one that is completely disconnected, you should ____________. A. gently tap the body with a screwdriver B. tag it ... insulated fuse puller D. short circuit the terminals to make sure that the capacitor is discharged
Description : All electric cables passing through watertight bulkheads must be _____________. A. installed with watertight stuffing tubes B. grounded on both sides of the bulkhead C. fitted with unions on each side of the bulkhead D. welded on both sides of the bulkhead
Description : According to Coast Guard Regulations (46 CFR), the talking and calling circuits of a sound powered telephone system must be _____________. A. intrinsically safe B. independent of each other C. independently grounded D. connected to a common ground
Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection
Description : When a megohmmeter is being used on a alternating current machine, the meter pointer will dip toward 'zero' and then gradually rise to the true resistance value if the motor insulation is _____________. A. grounded B. good C. shorted D. dirty
Description : Violent gassing from a lead-acid battery while it is being charged, indicates that the _____________. A. plate separators are grounded B. battery compartment ventilation is inadequate C. electrolyte specific gravity is too low D. charging rate is too high
Description : To determine if a stator coil is grounded, you should use a/an _____________. A. ammeter B. ground detection lamp C. magneto D. megger
Description : A grounded switch or cable will be indicated by a megohmmeter reading of _____________. A. infinity B. 'zero' C. being unsteady in the high range D. being unsteady in the low range
Description : While starting a main propulsion synchronous motor, the ammeter pegs out at maximum and then returns to the proper value after synchronization. This indicates the _____________. A. motor has started ... field windings are grounded C. slip rings are dirty D. power transmission cables are grounded
Description : If a voltage tester is being used to check for defective fuses in the circuit, shown in the illustration, which of the readings will indicate that fuse #2 is open? EL-0062 A. C-B full voltage B. A-D full voltage C. A-D no voltage D. C-B no voltage
Description : In the lighting distribution circuit shown in the illustration, if all switches are closed and fuse 'F2' were to open, all lights on branches ____________. EL-0013 A. '1', '2', and '3' would go out B. '1' ... and '3' would burn dimly D. '1' and '3' would go out, while branch '2' would remain lit
Description : When changing fuses, you should always _____________. A. wear rubber boots B. use a fuse puller C. stand on a rubber mat D. wear safety glasses
Description : In order to determine whether or not 'fuse 2' shown in the illustration is defective, you should connect the voltage tester leads across points _____________. EL-0062 A. AC B. AD C. BC D. BD
Description : In order to determine whether or not 'Fuse 1', shown in the illustration is defective, you should connect the voltage tester leads across points _____________. EL-0062 A. AC B. AD C. BC D. BD
Description : A fuse will 'blow' if _____________. A. an electric motor is stopped suddenly by opening a switch B. the flow of current to the protection device is reversed C. the electrical current exceeds the rated value of the fuse D. unequal resistors are connected in parallel
Description : Since fuse elements are made of zinc or any alloy of tin and lead, the melting point of the fuse element must be _____________. A. higher than that of copper B. lower than that of copper C. equal to that of copper D. reached when the conductor it is protecting becomes 'white hot.'
Description : A fuse that blows often should be replaced only with a fuse of _____________. A. the recommended current and voltage rating B. higher current and voltage rating C. higher current and lower voltage rating D. lower current and higher voltage rating
Description : A tubular fuse should always be removed from a fuse panel with _____________. A. a screwdriver B. a pair of insulated metal pliers C. any insulated object D. fuse pullers
Description : Before servicing the device indicated as 'A' in panels #1 and #3 of the illustration, the device labeled 'CT' must __________. EL-0003 A. have the disconnected leads taped to prevent ... D. have one lead grounded to discharge static electricity for the prevention of damage to electronic components
Description : A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start
Description : When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately, or the resultant flashing may _____________. A. blow the lamp's circuit breaker B. explode, ... fly in all directions C. short circuit the ballast transformer D. damage the starter and the ballast
Description : With both ends of a three conductor cable disconnected and arranged without the conductors touching each other, an ohmmeter reading of 'zero' ohms between the ends of one conductor would indicate _____________. A. continuity B. a partial ground C. the resistance is infinite D. a short circuit
Description : Fuses placed in series with a thermal trip-type circuit breaker are used for _____________. A. time-delay protection B. short-circuit protection C. short duration surge protection D. sustained overload protection
Description : A low-voltage protection circuit is used in electric motor starting equipment to _____________. A. trip circuit contactors when the motor overspeeds due to low voltage B. trip circuit ... voltage without manually resetting D. prevent the motor from restarting automatically on restoration of voltage
Description : To properly use a hook-on-type volt/ammeter to check current flow, you must FIRST _____________. A. de-energize the circuit to allow connection of the instrument in series B. hook the jaws ... test leads to the appropriate terminals D. short the test leads and calibrate the instrument to zero
Description : Temporary repairs to an open DC propulsion armature coil can be made by _____________. A. connecting the coil ends directly to a pair of negative brushes B. disconnecting coil ends, insulating ... C. grounding the coil ends and short circuiting the commutator bar D. removing the sparking brushes
Description : The circuit illustrated represents a 2 wire DC ground detecting system. If the positive bus is grounded and the test button is pushed, which of the lamps will be brightest? EL-0008 A. X B. Y C. both will be equal brightness. D. both will go out.
Description : What is the direction of current through the load resistor in the circuit shown in the illustration? EL-0085 A. Always from point 'Z' to the grounded end. B. Always from the grounded end to ... on the instantaneous polarity at point 'W'. D. It cannot be determined without a directional ammeter.