WorksheetsElectricidad 2
Total questions: 49
Worksheet time: 25mins
On a vessel with turbo-electric drive, which of the following conditions would indicate that the propulsion motor had dropped out of synchronization with the propulsion generator?
Excessive vibration of the vessel
Tripped main motor interlocks
Overheated crosstie busses
Closed contact in the field circuits
Electric coupling excitation is reduced at slow speeds to __________.
increase speed control
increase shaft torque
prevent coupling overheating
prevent coupling slippage
Brushless generators are designed to operate without the use of __________.
brushes
slip rings
commutators
all of the above
Low horsepower, polyphase, induction motors can be started with full voltage by means of __________.
compensator starters
auto-transformer starters
across-the-line starters
primary-resistor starters
Moisture damage, as a result of condensation occurring inside of the cargo winch master switches, can be reduced by __________.
installing a light bulb in the pedestal stand
coating the switch box internals with epoxy sealer
venting the switch box regularly
using strip heaters inside the switch box
In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by __________.
a manual override switch
the weight of the load on the boom
a spring set brake
a hand operated band brake
Which of the following statements represents the main difference between a relay and a contactor?
Contactors control current and relays control voltage.
A relay is series connected and a contactor is parallel connected.
Contactors can handle heavier loads than relays.
Contactors are made from silver and relays are made from copper.
The electrolyte used in a nickel-cadmium battery is distilled water and __________.
diluted sulfuric acid
potassium hydroxide
lead sulfate
zinc oxide
A resistance in a circuit of unknown value is to be tested using the voltmeter/ammeter method. Therefore, the meters should be connected with __________.
both meters in series with the resistance
both meters in parallel with the resistance
the ammeter in series and the voltmeter in parallel with the resistance
the ammeter in parallel and the voltmeter in series with the resistance
The purpose of a short circuit forcing module (short time trip) installed in a branch line is to provide __________.
high speed clearance of low impedance short circuits in the branch
continuity of service on main bus under short circuit conditions in a branch
isolation of short circuits by selective tripping of branch circuit breakers
all of the above
You are performing an out-of-circuit test of the semi-conductor shown in the illustration. Using an ohmmeter on 'low power' position and with leads properly installed, which of the listed results would indicate a good Collector-Base junction?
A low reading with red lead on "A" and black lead on "C"; and a high reading with the leads reversed.
A low reading with red lead on "A" and black lead on "B"; and a high reading with the leads reversed.
A low reading with black lead on "A" and red lead on "B"; and a high reading with the leads reversed.
A low reading with black lead on "A" and red lead on "C"; and a high reading with the leads reversed.
To properly use a hook-on-type volt/ammeter to check current flow, you must FIRST __________.
de-energize the circuit to allow connection of the instrument in series
hook the jaws of the instrument around the insulated conductor
connect the voltage test leads to the appropriate terminals
short the test leads and calibrate the instrument to zero
Autotransformer starters or compensators are sometimes used with polyphase induction motors to __________.
reduce the voltage applied to the motor during the starting period
increase the voltage for 'across-the-line starting'
provide a backup means of voltage regulation for emergency starting
allow the voltage to be either stepped up or down, depending on the application, to ensure full torque
When troubleshooting electronic equipment, you should use a high impedance multimeter __________.
to prevent excess current flow through the meter that would damage it
for AC measurements only and a low resistance meter for DC measurements
whenever a low impedance meter is not available, regardless of the components being tested
so as not to load down the circuit and obtain erroneous voltage readings
The amount of voltage induced in the windings of an AC generator depends on __________.
the number of conductors in series per winding
the speed at which the magnetic field passes across the winding
the strength of the magnetic field
all of the above
When reading electrical motor controller diagrams, it helps to know that __________.
current paths in the control circuit are drawn as heavy lines and in the power circuit as lighter lines
current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines
circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter lines
circuits subject to 500 volts or greater are drawn as light lines and below 500 volts as heavy lines
A tubular fuse should always be removed from a fuse panel with __________.
a screwdriver
a pair of insulated metal pliers
any insulated object
fuse pullers
Which of the motors for the devices listed below is fitted with an instantaneous overload relay?
Fan
Pump
Winch
Machine tool
Which of the following statements concerning analog and digital devices are correct?
The variables in digital systems are fixed quantities, and the variables in analog systems are continuous quantities.
There are no basic differences between the two systems.
Analog devices are superior in accuracy compared to digital devices.
Operations in a digital device are performed simultaneously.
The Wheatstone bridge is a precision measuring instrument utilizing the principle of changes in __________.
inductance
capacitance
resistance
amperage
Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel cage motor does not?
Slip rings
End rings
A centrifugal switch
End plates
Which of the listed logic gates is considered to be a BASIC building block (basic logic gate) used in logic diagrams?
NAND
OR
NOR
All of the above.
What operational characteristics do the components labeled as "S" and "R" represent in the motor controller diagram shown in the illustration?
Standard and Reverse directions
Stop and Restart features
Subnormal and Regular loading
Start and Run functions
An electrical device which prevents an action from occurring until all other required conditions are met is called a/an __________.
limit
monitor
modulator
interlock
The electrolyte in a lead-acid storage battery consists of distilled water and __________.
hydrogen chloride
calcium chloride
sulfuric acid
muriatic acid
As a general rule, the first troubleshooting action to be taken in checking faulty electric control devices is to __________.
draw a one line diagram of the circuitry
test all fuses and measure the line voltage
take megger readings
insulate the apparatus from ground
Which of the following statements describes the significance of ambient temperature in relation to the service life of electronic components?
Ambient temperature should be as high as possible to drive off moisture.
Increased ambient temperature decreases the service life of electronic components.
Ambient temperature is not significant as long as the relative humidity is kept low.
A reduced ambient temperature causes a corresponding reduced service life.
The load sharing characteristics of two diesel generators operating in parallel are mostly dependent on their governor __________.
load limit settings
idle speed settings
speed limit settings
speed droop settings
Tightly knit metal braid wire can be used with a printed circuit board when __________.
conductor resistance is not a factor
required to desolder components on the board
electrically produced magnetic fluxes would cause inaccuracies in adjacent components
reactance in the circuit must be kept to a minimum
In an AC generator, direct current from a separate source is passed through the windings of the rotor __________.
by means of slip rings and brushes
by means of a commutator
by means of rotating bar magnet
to minimize the danger of arc over
Which of the listed procedures should be carried out to prevent moisture damage to electrical apparatus during extended periods of idleness?
Fill the motor housing with CO2 to inert the space.
Strap silica gel around the commutator.
Place heat lamps in the motor housings.
Cover the equipment with a canvas tarpaulin.
Electric strip heaters are used in motor controllers to __________.
prevent freezing of movable contacts
keep the components at their design ambient temperature
prevent condensation of moisture
minimize resistance in internal circuits
A fuse that blows often should be replaced only with a fuse of __________.
the recommended current and voltage rating
higher current and voltage rating
higher current and lower voltage rating
lower current and higher voltage rating
The freezing point of the electrolyte in a fully charged lead-acid battery will be __________.
higher than in a discharged battery
lower than in a discharged battery
the same as in a discharged battery
higher than in a discharged battery, but the specific gravity will be less
The heating of conductors as a result of resistance in a distribution circuit causes a power loss expressed as __________.
line droop
line loss
IR drop
hysteresis
The output voltage of a three-phase alternator is regulated by the __________.
AC voltage to the armature
AC voltage to the field
DC voltage to the armature
DC voltage to the field
In a cartridge-type fuse, the metal element is contained in a __________.
porcelain window
thermal cut out
fiber tube
flasher device
The proper way to apply plastic electrical tape to an electric cable splice is to __________.
apply tape to the braided cover, but avoid touching it
wind the tape so that each turn overlaps the turn before it
apply the tape in one non-overlapping layer only
heat the tape with a soldering iron for good bonding
Time delayed or delayed action-type fuses are designed to __________.
prevent grounds in branch circuits
prevent opens in motor circuits
permit momentary overloads without melting
guard lighting and electronic circuits
Which of the following statements best describes the material known as varnished cambric?
Felted asbestos sealed with varnish.
Cotton cloth coated with insulating varnish.
Rubber insulation coated with a layer of tin.
Paper impregnated with mineral oil, specially wrapped with nonmetallic tape, and coated with varnish.
The part of a fuse that melts and opens an electrical circuit is typically made of __________.
copper and antimony
steel and babbitt
aluminum or beryllium alloy
zinc or an alloy of tin and lead
To effectively clean a commutator in good physical condition, you should use __________.
trichloride ethylene
kerosene
a canvas wiper
a commutator stone
The main difference between a motor control circuit containing low voltage release and low voltage protection is that the latter contains __________.
a magnetic operating coil
normally open line contacts
thermal-overload protection
a momentary-contact start button
When charging lead-acid batteries, you should reduce the charging rate as the battery nears its full charge capacity to __________.
prevent excessive gassing and overheating
allow equalization of cell voltages
reduce lead sulfate deposits
increase lead peroxide formation
Before reassembling any machinery, you should __________.
replace all bearings regardless of length of service
apply a heavy coat of oil to all mating surfaces
clean any corroded surfaces and file all burrs smooth
coat all parts with alemite grease
The type of feature afforded auxiliaries vital to the operation of propelling equipment, where automatic restart after a voltage failure would not create a hazard, is termed __________.
low voltage protection
high amperage protection
low voltage release
high amperage release
Which of the following statements correctly applies to transistors?
LED and LCD are the two basic types of transistors.
The three terminals are called the emitter, base, and collector.
The emitter separates the base and collector.
The collector separates the emitter and base.
The basic measuring unit of inductance is the __________.
coulomb
ohm
farad
henry
The purpose of DC generator brushes is to __________.
neutralize armature reaction
conduct electric current to an outside circuit
convert DC current to AC current
provide excitation to a DC generator
