奥鹏作业网西交《专业英语》在线作业
试卷总分:100 得分:100
一、单选题 (共 30 道试题,共 60 分)
1.Resistors are ( ) elements.
A.passive
B.independent sources
C.dependent sources
D.active
2.An electric heater draws 10 A from a 120V line. The resistance of the heater is ( ).
A.1.2?
B.1200?
C.120?
D.12?
3.The algebraic sum of all voltages around a loop is ( ).
A.zero
B.sum of voltage rises
C.sum of voltage drops
D.indefinite value
4.ON-OFF information can be represented by ( ) signal.
A.an analog
B.a discrete
C.a digital
D.a control
5.The process quantizing the continuous values into a binary scale is called ( ).
A.digital-to-digital conversion
B.digital-to-analog conversion
C.analog-to-digital conversion
D.analog-to-analog conversion
6.The wide application of operational amplifiers lies in advantage of using ( ).
A.small output impedance
B.positive feedback networks
C.negative feedback networks
D.large open-circuit gain
7.When an induction motor with 10 poles is supplied by 50Hz three-phase ac power source, the synchronous revolutions per minute is ( ). (Synchronous r/min = 120 f/p)
A.900
B.700
C.600
D.1000
8.The electric machine that operates at speeds above synchronous speed works in ( ) region.
A.stopping
B.plugging
C.motoring
D.generating
9.A transformer is a device that can convert one ac voltage to another ac voltage through the action of ( ).
A.an electric field
B.an electric circuit
C.a magnetic field
D.a coupling circuit
10.The primary winding is connected to ( ).
A.the power source
B.the motor
C.the measurement instrument
D.the load
11.Copper losses are ( ) losses in the primary and secondary windings of the transformer core.
A.resistive
B.reactive
C.inductive
D.capacitive
12.( ) can provide an asynchronous link between two ac electric power system with different nominal frequencies.
A.The HVDC (high voltage DC) transmission
B.The EHV (extra-high voltage) AC transmission
C.The AC distribution
D.Generators
13.The generator voltages are usually stepped up to the transmission voltage level by ( ).
A.step-up transformers
B.step-down transformers
C.series capacitor
D.parallel reactors
14.The objective of the optimal economic operation of power systems is ( ).
A.to minimize the total production cost
B.to maintain voltages constant
C.to maintain frequency constant
D.to ensure balance between generation and load
15.Any protection scheme consists basically of ( ).
A.two elements
B.three elements
C.four elements
D.five elements
16.The protective scheme that senses zero sequence current and operates as necessary is called as ( ).
A.zero sequence protection
B.overcurrent protection
C.negative sequence protection
D.directional protection
17.The distance protection is applied to protect ( ).
A.transmission lines
B.transformers
C.generators
D.buses
18.The thermal energy of the steam is converted into ( ) energy by the turbine.
A.potential
B.mechanical
C.electrical
D.chemical
19.( ) is used as coolant in light-water reactors.
A.Water
B.Organic compound
C.Molten salt
D.Gas
20.In the form of ( ) the output is continuously fed back and compared with the reference input.
A.sampled-data control
B.discrete-data control
C.discontinuous control
D.continuous control
21.The overall transfer function is the ratio of the transform of the controlled variable to the transform of ( ).
A.the reference input
B.the output variable
C.the feedback
D.the controlled variable
22.The system’s characteristic equation can be used to determine ( ) of a linear time-invariant system.
A.the stability
B.the observability
C.the controllability
D.magnitude of the steady-state error
23.In the root-locus method the actual time response of a system can be obtained by means of ( ).
A.the inverse Laplace transform
B.the inverse Fourier transform
C.the Laplace transform
D.the Fourier transform
24.The Buck(降压式变换器) is a ( ) converter.
A.voltage step-up
B.resistance
C.current step-up
D.current step-down
25.Most desktop computers use a separate ( ) as a display device, where notebook computers use a flat panel LCD screen (liquid crystal display screen) that attached to the system unit.
A.keyboard
B.hard disk
C.Mouse
D.Monitor
26.A desktop computer’s sound card sends signals to external ( ).
A.speaker
B.printer
C.keyboard
D.Modem
27.Data stored in RAM ( ) when the power of the computer is turned off.
A.temporarily disappears
B.permanently disappears
C.is held temporarily
D.is held permanently
28.The notebook computers use ( ) as standard display equipment.
A.TV screen
B.LED
C.LCDs
D.CRT display
29.Image clarity on a computer screen is measured with ( ).
A.screen size
B.resolution
C.dot pitch
D.color depth
30.( ) that connects at least two networks makes decision about the best route for data.
A.A router（路由器）
B.A network card
C.A modem
D.A hub
二、完型填空 (共 2 道试题,共 40 分)
40.##the direct current is useful, it has one great##, that is, there is no easy, economical way to increase or decrease its ##. The alternating current has not this disadvantage.##a special device, it is##to transform a high voltage into a## voltage or a low voltage into a high voltage. The##that we use to transform the voltage is called a##. The alternating current can ##be changed easily into the direct current. The device which can do this is spoken of as a## .
(1).
A.For
B.As
C.Although
D.Also
(2).
A.thing
B.meaning
C.disadvantage
D.advantage
(3).
A.voltage
B.resistance
C.current
D.capacitance
(4).
A.Using
B.Marking
C.Making
D.Having
(5).
A.possible
B.impossible
C.easy
D.different
(6).
A.small
B.low
C.large
D.high
(7).
A.thing
B.one
C.machine
D.device
(8).
A.transformer
B.transfer
C.charge
D.change
(9).
A.hard
B.easily
C.but
D.also
(10).
A.remote
B.refiner
C.rectifier
D.receiver
50.There are##inds of current: direct current (DC) and alternating##(AC). A direct current is a current flowing in a##always in one direction.##alternating current is a current##changing its direction of flow. The electric current##through electric##lines is##current. This is because AC is easy to##and more economical when we transmit it over long ## .
(1).
A.two
B.three
C.one
D.four
(2).
A.current
B.currency
C.conductor
D.coincidence
(3).
A.semiconductor
B.current
C.currency
D.conductor
(4).
A.The
B.That
C.An
D.A
(5).
A.timely
B.second
C.probably
D.periodically
(6).
A.unlighted
B.transported
C.transmitted
D.transformed
(7).
A.power
B.powder
C.poured
D.energy
(8).
A.always
B.alternative
C.alternating
D.alter
(9).
A.control
B.console
C.consider
D.consent
(10).
A.way
B.time
C.distances
D.ago
