Electrical 3
Electrical Wiring and Motor Fundamentals Quiz
Test your knowledge on electrical wiring, insulation materials, and motor operation with this comprehensive quiz. It covers essential concepts that are vital for anyone working in the electrical field.
- 35 multiple-choice questions
- Focus on electrical safety and materials
- Perfect for professionals and learners alike
Which of the following statements concerning copper wire sized by AWG numbers is correct?
Number 10 AWG wire has a higher dielectric strength than 12 AWG wire.
Number 12 AWG wire at 25°C has more resistance per 1000 ft than 10 AWG wire at 25°C.
Number 12 AWG wire has a higher current rating than 10 AWG wire.
Number 12 AWG wire is larger than number 10 AWG wire.
A conductor with a cross-sectional area of one circular mil would have a diameter of __________.
0.001 inches
0.01 inches
0.1 inches
0.0001 inches
Which of the following materials is a good electrical insulator?
Copper
Silver
Wood
Gold
A common type of protective covering used on electrical conductors is __________.
Silver sheathing
Rubber or plastic
Plain paper
Babbitt sheathing
Which of the following statements best describes the material known as varnished cambric?
Rubber insulation coated with a layer of tin.
Cotton cloth coated with insulating varnish.
Felted asbestos sealed with varnish.
Paper impregnated with mineral oil, specially wrapped with nonmetallic tape, and coated with varnish.
Which of the listed classes of electrical insulation is suited for the highest operating temperature?
Class 130 (B)
Class 105 (A)
Class 90 (O)
Class 180 (H)
Most conducting materials such as copper, aluminum, iron, nickel, and tungsten __________.
Decrease in resistance with increased temperature
Increase in resistance with decreased temperature
Increase in resistance with increased temperature
Increase in conductance with increased temperature
The reason some electric cables are formed of stranded wire is to __________.
Decrease the weight for a given size wire
Increase their flexibility
Increase the current carrying capability for a given size wire
Assure good conductivity at junction points
Which of the following characteristics is most critical in determining the size of the cable to be used in a particular circuit?
Current rating
Weight per unit length
Voltage rating
Inductance per unit length
The existing resistance of a conductor is dependent upon its length, cross-sectional area, __________.
Capacitive reactance and material
Material and insulation
Inductive reactance and insulation
Material and temperature
Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct?
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.
Wire must be copper stranded.
Each wire must be 14 AWG or larger, regardless of locations and use.
All of the above.
The resistance of a conductor varies __________.
Directly as its length and directly as its cross-sectional area
Inversely as its length and directly as its cross-sectional area
Directly as its length and inversely as its cross-sectional area
Inversely as its length and inversely as its cross-sectional area
The resistance of electric wire will decrease as its __________.
Temperature increases
Cross-sectional area increases
Length increases
Percent of metallic purities increases
When the current flow through a copper wire increases, its __________.
Temperature will increase
Insulation will burn
Resistance will decrease
Conductivity will increase
A wire is being used as a replacement having twice the length and one-half the cross-sectional area of the original wire. The resistance of this new wire, when compared to that of the original wire, is __________.
The same as the original resistance
Twice as much
Four times as great
One-half of the original resistance
The proper way to apply plastic electrical tape to an electric cable splice is to __________.
Apply the tape in one non-overlapping layer only.
Wind the tape so that each turn overlaps the turn before it.
Apply tape to the braided cover, but avoid touching it.
Heat the tape with a soldering iron for good bonding.
Which of the following statements about copper wire sized by the AWG rating is correct?
Number 12 AWG wire is larger than Number 10 AWG wire.
Number 10 AWG wire has a higher dielectric strength than number 12 AWG wire.
Number 12 AWG wire has a higher current rating than number 10 AWG wire.
Number 12 AWG wire at 25°C has more resistance per 1000 feet than No. 10 AWG wire at 25°C.
The heating of conductors as a result of resistance in a distribution circuit causes a power loss expressed as __________.
IR drop
Line loss
Line droop
Hysteresis
In a three-phase, squirrel-cage type, induction motor, the primary rotating magnetic field is established by the __________.
Current induced in the rotor windings
Application of a three-phase voltage supply to the stator windings
Laminated steel core and aluminum conductors in the rotor
Interaction of the magnetic field caused by the induced current in the squirrel-cage bars with the magnetic field of the stator
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
The speed of a three-phase squirrel-cage induction-type motor operating in a fixed frequency system is varied by changing the
Number of phases to the motor
Number of stator poles
Locked rotor current
Resistance of the rotor winding
If there is a reduction in the normally supplied frequency to a 120/240 volt, three-phase AC current motor from 60 hertz to 55 hertz, the motor would
Run at a slower speed
Operate at a lower current
Vibrate excessively
Trip off the line
In a 15 HP induction-type motor with a squirrel cage rotor, the current required at standstill to produce starting torque is approximately
Half the full load current
Equal to the full load current
Five times the full load current
Ten to twenty times the full load current
If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will continue to run, but will
Vibrate and have reduced torque
Speed up due to the reduced number of poles
Run cooler due to reduced current flow
Stop
If a three-phase induction motor malfunctions and drops to a single-phase (one supply line open) __________.
The motor will continue to run if it is not heavily loaded
More torque will be developed
The motor will immediately stop and not be able to be restarted
The motor will immediately stop and can only be restarted at no load
A characteristic of a wound-rotor induction motor, with a high resistance rotor winding, is __________.
Low starting torque
High starting torque
High speed
Low starting voltage
Regarding an induction motor, the power developed by the rotor automatically adjusts itself to the __________.
Power required to drive the load
Speed required to drive the load
Current flow in the motor stator
Torque developed by the rotating field
The synchronous speed of an induction motor is the __________.
Speed at which the rotor turns
Speed of the rotating field
Frequency of the rotor current
Slip in per cent of rotor RPM
The direction of rotation of an induction motor is __________.
Opposite the rotating field direction
The same as the direction of the rotating field
Determined by the number of poles
Determined by the staggering of the brushes
One item listed on the name plate of a cargo pump motor is 'degrees centigrade rise.' This number is based on
Normal temperature change from cold to hot
An ambient temperature of 40°C
Minimum heat rise from no load to full load
Maximum degrees centigrade rise from absolute zero
The rotor of a synchronous motor operates in synchronism with the rotating field because __________.
Of the amortisseur windings
The rotor is magnetically locked into step with the rotating magnetic field by the excitation current
The field strength varies directly with rotor slip
The stator flux rotates in the opposite direction
The most common source of excitation for the rotor of a synchronous motor is a/an
Step-up transformer
Half-wave rectifier
DC supply
AC supply
The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to
Provide excitation to the DC field
Start the machine as an induction motor
Contribute extra torque at synchronous speed
Prevent the machine from falling out of step
The speed of a synchronous motor is varied by __________.
Interchanging any two of the three live leads
Changing the voltage of the system
Changing the input frequency
Increasing the field excitation
Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency?
A four-pole synchronous motor under normal load.
A four-pole induction motor under no load.
A six-pole synchronous motor under normal load.
A six-pole induction motor under full load.
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