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WorksheetsElectricidad 10
Total questions: 50
Worksheet time: 25mins
When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must __________.
insulate the field frame from the ship's hull
disconnect each shunt field coil before testing
use a motor driven high capacity megohmmeter
remove all main line lead connections before testing
As shown in the illustration, which of the operations listed will happen when the 'jog button' is pushed?
Coil 'CR' closes the normally open 'CR' contacts.
Coil "M" opens contact "M".
Coil "M" closes contact "M".
Contact "M" remains open despite the jog button being pushed.
The most practical method used for resurfacing a ship's main propulsion motor commutator is to __________.
turn it down in the ship's lathe
use a grinding rig
use a hand stone
burnish it with commutator stones
Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ________
armature winding speed
inductance load drop
coil pitch factor
armature reactance voltage drop
The division of the reactive KVA load between paralleled AC generators is initiated by the __________.
prime mover governors
voltage regulators
phase balance relay
proportioner
Which of the following losses is/are present in every direct current generator armature?
Winding copper loss
Core eddy current loss
Magnetic hysteresis loss
All of the above.
The most common type of AC service generator found aboard ship is the stationary __________.
electromagnetic field, revolving armature type
electromagnetic field, oscillatory armature type
armature, oscillatory electromagnet field type
armature, rotating electromagnetic field type
Which of the following statements is correct for the illustrated circuit?
'R1', 'R2', and 'R3' are connected in series.
'R1', 'R2', and 'R3' are connected in parallel.
The voltages measured across 'R1', 'R2', and 'R3' are equal.
The total resistance equals 1/R1 + 1/R2 + 1/R3.
Which of the following statements about a three-phase wye connection is correct?
The line current is 1.73 times the phase current.
The phase current is 1.73 times the line current.
The line voltage is 1.73 times the phase voltage.
The phase voltage is 1.73 times the line voltage.
Ambient temperature is the __________.
amount of permissible temperature rise
amount of temperature developed by an operating motor
normal operating temperature, less the room temperature
temperature of the immediate surroundings
When measuring AC current flow, you must always connect the meter __________.
in series with the power source and load
in parallel with the power source and load
insuring correct polarity
using the lowest range possible to prevent instrument damage
To conduct an in-circuit test of a transistor, you should use a/an __________.
voltmeter or transistor tester
impedance meter
ohmmeter or transistor tester
wattmeter
Which of the spaces listed is defined as a 'location requiring an exceptional degree of protection' when considering the installation of shipboard electrical equipment?
Machinery space
Chart room
Console room
Accommodation space
The emergency electrical power source on tank vessels over 500 GT on an international voyage, should be capable of continuous operation under emergency load for __________.
6 hours
12 hours
18 hours
24 hours
Which of the following statements concerning electrical cables is correct?
Where they pass through watertight bulkheads, they should be fitted with watertight stuffing boxes.
Electric cable coverings should never be grounded.
Electrical cables must be rigidly held in place by welding of armored cable, or glued in place where nonmetallic insulation is used.
All of the above.
Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced?
Short out the fuse before removing it from the circuit.
Use needle-nose pliers to remove fuse from the circuit.
Replace blown fuse with one of equal voltage and ampere capacity.
Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.
When maintenance personnel are working on electrical equipment, all supply switches should be secured in the open position and tagged specifically by the __________.
watch engineer
chief engineer or first assistant
chief electrician
person performing the repair
AC and DC generators are similar in that they __________.
both initially generate alternating voltages
both rectify the voltage before delivery
are constructed at the same physical size for the same kilowatt rating
both supply three-phase power
Motor starter or controller contacts may become welded together if the contacts __________.
open too quickly and arc
close under excessive pressure
open or close too quickly
close under excessive starting current
During discharge of a lead-acid storage battery, which of the following actions occurs?
The acid becomes stronger.
Both plates change chemically to ammonium chloride.
The acid becomes weaker.
Hydrogen gas is liberated.
If the length of a wire is halved and the cross-sectional area is doubled, the resistance will be __________.
quartered
unchanged
doubled
quadrupled
Which of the following devices are protected from being motorized by a reverse-power relay?
Alternators
Wave guides
Exciters
Amplidynes
If many turns of an alternating current coil for a contactor become short circuited, the coil __________.
temperature will drop
will probably burn out immediately
will continue to operate
will operate on reduced current
Relative to the secondary winding of a step-up transformer, the primary winding will have __________.
more turns
fewer turns
same number of turns but smaller wires
twice as many turns
Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct?
Each wire must be 14 AWG or larger, regardless of locations and use.
Wire must be copper stranded.
The only wire that does not have to be in a suitable enclosure or cover is the ground wire used with portable tools and lights.
All of the above.
Which of the following statements is/are true regarding requirements for receptacle outlets aboard vessels?
Each receptacle outlet operating at 100 volts or more must have a grounding pole.
Outlets connecting a lifeboat and the vessel's electrical system must have threaded plugs.
Machinery spaces must contain sufficient outlets for lighting all machinery with a portable light having a 50 foot flexible cord.
All of the above.
An emergency generator, driven by an internal combustion engine, shall be tested under load for a minimum of 2 hours at least once every __________.
week
2 weeks
month
3 months
Which of the following methods of finish applications is/are considered to be satisfactory for resisting corrosion?
Electroplating with cadmium
Sherardizing
Galvanizing
All of the above
When there is a fire in a large electric motor, normally the very FIRST step is to __________.
secure the electric supply
ventilate area to remove smoke
start the fire pump and lead out hose
apply foam
Corrosion-resistant material' and 'non-corrodible material' will include which of the following __________.
brass
copper-nickelplastics
plastics
all of the above
To equalize the power factor of two alternators operating in parallel, the __________.
field excitation of both units is adjusted
governors of both units are adjusted
phase sequence is altered
kilowatt load is evenly divided
When the voltage remains constant and the resistance is increased in a series circuit, the flow of current __________.
increases by the square of the original value
increasesremains the same
remains the same
decreases
A DC ammeter is always connected __________.
in series with a circuit
in parallel with a circuit
with internal shunts only
without regard to polarity
Under which of the following conditions will a lead-acid battery be given a 'test discharge'?
To determine its capacity.
Whenever a cell cannot be brought within 10 points of full charge specific gravity.
When one or more cells is found to have less than normal voltage after an equalizing charge.
All of the above.
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 a DC motor are reversed?
The motor will not start.
The direction of rotation of the armature will be reversed.
The direction of rotation of the armature will remain the same.
The field pole windings will become overheated.
When a console indicating lamp burns out, attempts to renew it should not be made while maneuvering because __________.
the new lamp may be of a higher wattage and cause heat damage to the lens
removing a faulty lamp usually causes an alarm to sound on the bridge
attention should be paid only to engine orders
a socket/wiring fault may cause a ground or short circuit to shut down a vital function
What is the approximate voltage per cell produced by the nickel-iron (Edison) battery?
0.85 volts
1.35 volts
2.20 volts
6.05 volts
Proper storage battery maintenance includes __________.
keeping connections tight and casing surfaces clean
making sure electrolyte level is below the separator plates
insulating the terminals with naval jelly
maintaining a high charging rate at all times
When checking for a possible single phase condition in a three-phase induction motor circuit, which of the following electrical measuring devices would be the most practical to use to locate the malfunction?
Meggar
amp-probe
growler
All of the above.
The standard method of controlling the output voltage of a 440 volt, 60 Hz, AC generator is accomplished by adjusting the __________.
prime mover speed droop
number of poles
alternator field excitation
load on the alternator
An accidental path of low resistance which passes an abnormal amount of current is known as a/an __________.
polarized ground
short circuit
ground reference point
open circuit
As shown in the illustration, which of the listed types of motor controllers and starters is indicated?
Across-the-line
Capacitor
Auto-transformer
Part-winding
In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to __________.
increase in speed
decrease in speed
affect generator speed only
affect main motor speed if done in conjunction with higher generator engine speeds
A semiconductor that decreases in resistance with an increase in temperature is known as a __________.
resistor
thermistor
diode
thermopile
An operating characteristic appearing on the name plates of shipboard AC motors is __________.
type of overload protection
rated slip
temperature rise
locked rotor torque
External shunts are sometimes used with ammeters to __________.
increase meter sensitivity
permit shunts with larger resistances to be utilized
prevent damage to the meter movement from heat generated by the internal shunt
reduce reactive power factor error
Which of the following statements represents an application of a silicon controlled rectifier?
Provides DC power for a main propulsion motor.
Used as a voltage reference diode.
Used in photo cell sensor circuits for boiler burners.
Used to eliminate AC power supply hum.
What damage may occur to the components of a winch master control switch, if the cover gasket becomes deteriorated?
Overheating of the winch motor.
Contamination of lube oil.
Sparking at the winch motor brushes.
Rapid corrosion of switch components.
In general, polyphase induction motors can be started on full line voltage by means of __________.
compensator starters
auto-transformer starters
across-the-line starters
primary-resistor starters
A direct current passing through a wire coiled around a soft iron core is the description of a simple __________.
magnetic shield
electromagnet
piezoelectric device
electromagnetic domain
