西交19秋《专业英语》在线作业
西交《专业英语》在线作业1.[单选题]Resistors are () elements.
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A.passive
B.active
C.independent sources
D.dependent sources
正确答案:——A——
2.[单选题]An electric heater draws 10 A from a 120V line. The resistance of the heater is ().
A.1200?
B.120?
C.12?
D.1.2?
正确答案:——C——
3.[单选题]The algebraic sum of all voltages around a loop is ().
A.zero
B.indefinite value
C.sum of voltage rises
D.sum of voltage drops
正确答案:——A——
4.[单选题]ON-OFF information can be represented by () signal.
A.a digital
B.an analog
C.a discrete
D.a control
正确答案:————
5.[单选题]The process quantizing the continuous values into a binary scale is called ().
A.digital-to-analog conversion
B.digital-to-digital conversion
C.analog-to-digital conversion
D.analog-to-analog conversion
正确答案:————
6.[单选题]The wide application of operational amplifiers lies in advantage of using ().
A.positive feedback networks
B.large open-circuit gain
C.negative feedback networks
D.small output impedance
正确答案:————
7.[单选题]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.1000
B.900
C.700
D.600
正确答案:————
8.[单选题]The electric machine that operates at speeds above synchronous speed works in () region.
A.motoring
B.generating
C.plugging
D.stopping
正确答案:————
9.[单选题]A transformer is a device that can convert one ac voltage to another ac voltage through the action of ().
A.an electric circuit
B.a magnetic field
C.an electric field
D.a coupling circuit
正确答案:————
10.[单选题]The primary winding is connected to (). 无忧答案网，q 761296021
A.the power source
B.the load
C.the measurement instrument
D.the motor
正确答案:————
11.[单选题]Copper losses are () losses in the primary and secondary windings of the transformer core.
A.inductive
B.capacitive
C.resistive
D.reactive
正确答案:————
12.[单选题]() 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
正确答案:————
13.[单选题]The generator voltages are usually stepped up to the transmission voltage level by ().
A.series capacitor
B.parallel reactors
C.step-up transformers
D.step-down transformers
正确答案:————
14.[单选题]The objective of the optimal economic operation of power systems is ().
A.to minimize the total production cost
B.to maintain frequency constant
C.to maintain voltages constant
D.to ensure balance between generation and load
正确答案:————
15.[单选题]Any protection scheme consists basically of ().
A.two elements
B.three elements
C.four elements
D.five elements
正确答案:————
16.[单选题]The protective scheme that senses zero sequence current and operates as necessary is called as ().
A.overcurrent protection
B.zero sequence protection
C.negative sequence protection
D.directional protection
正确答案:————
17.[单选题]The distance protection is applied to protect ().
A.transformers
B.generators
C.transmission lines
D.buses
正确答案:————
18.[单选题]The thermal energy of the steam is converted into () energy by the turbine.
A.electrical
B.mechanical
C.chemical
D.potential
正确答案:————
19.[单选题]() is used as coolant in light-water reactors.
A.Gas
B.Organic compound
C.Molten salt
D.Water
正确答案:————
20.[单选题]In the form of () the output is continuously fed back and compared with the reference input.
A.continuous control
B.discontinuous control
C.discrete-data control
D.sampled-data control
正确答案:————
21.[单选题]The overall transfer function is the ratio of the transform of the controlled variable to the transform of ().
A.the controlled variable
B.the reference input
C.the feedback
D.the output variable
正确答案:————
22.[单选题]The system’s characteristic equation can be used to determine () of a linear time-invariant system.
A.the stability
B.magnitude of the steady-state error
C.the controllability
D.the observability
正确答案:————
23.[单选题]In the root-locus method the actual time response of a system can be obtained by means of ().
A.the inverse Fourier transform
B.the inverse Laplace transform
C.the Fourier transform
D.the Laplace transform
正确答案:————
24.[单选题]The Buck(降压式变换器) is a () converter.
A.voltage step-up
B.current step-down
C.current step-up
D.resistance
正确答案:————
25.[单选题]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.Mouse
C.Monitor
D.hard disk
正确答案:————
26.[单选题]A desktop computer’s sound card sends signals to external ().
A.printer
B.speaker
C.Modem
D.keyboard
正确答案:————
27.[单选题]Data stored in RAM () when the power of the computer is turned off.
A.is held permanently
B.permanently disappears
C.is held temporarily
D.temporarily disappears
正确答案:————
28.[单选题]The notebook computers use () as standard display equipment.
A.CRT display
B.LCDs
C.LED
D.TV screen
正确答案:————
29.[单选题]Image clarity on a computer screen is measured with ().
A.screen size
B.dot pitch
C.resolution
D.color depth
正确答案:————
30.[单选题]() that connects at least two networks makes decision about the best route for data.
A.A modem
B.A network card
C.A hub
D.A router（路由器）
正确答案:————
31.[]##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.Also
B.Although
C.As
D.For
正确答案:————
(2)
A.meaning
B.thing
C.advantage
D.disadvantage
正确答案:————
(3)
A.resistance
B.capacitance
C.voltage
D.current
正确答案:————
(4)
A.Making
B.Marking
C.Using
D.Having
正确答案:————
(5)
A.possible
B.impossible
C.easy
D.different
正确答案:————
(6)
A.high
B.low
C.large
D.small
正确答案:————
(7)
A.thing
B.machine
C.one
D.device
正确答案:————
(8)
A.transfer
B.transformer
C.change
D.charge
正确答案:————
(9)
A.also
B.easily
C.hard
D.but
正确答案:————
(10)
A.receiver
B.remote
C.rectifier
D.refiner
正确答案:————32.[]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.one
B.two
C.three
D.four
正确答案:————
(2)
A.conductor
B.coincidence
C.current
D.currency
正确答案:————
(3)
A.current
B.currency
C.semiconductor
D.conductor
正确答案:————
(4)
A.A
B. An
C. The
D. That
正确答案:————
(5)
A.probably
B. periodically
C.timely
D.second
正确答案:————
(6)
A.transmitted
B.transported
C.transformed
D.unlighted
正确答案:————
(7)
A.powder
B.energy
C.poured
D.power
正确答案:————
(8)
A.alternative
B.always
C.alternating
D.alter
正确答案:————
(9)
A.consider
B.console
C.control
D.consent
正确答案:————
(10)
A.time
B.distances
C.way
D.ago
正确答案:————
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