2019秋西交《专业英语》在线作业1（100分）
【奥鹏】-[西安交通大学]西交《专业英语》在线作业试卷总分:100 得分:100
第1题,Resistors are () elements.
A、passive
B、active
C、independent sources
D、dependent sources
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第2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?
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第3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
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第4题,ON-OFF information can be represented by () signal.
A、a digital
B、an analog
C、a discrete
D、a control
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第5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
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第6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
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第7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
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第8题,The electric machine that operates at speeds above synchronous speed works in () region.
A、motoring
B、generating
C、plugging
D、stopping
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第9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
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第10题,The primary winding is connected to ().
A、the power source
B、the load
C、the measurement instrument
D、the motor
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第11题,Copper losses are () losses in the primary and secondary windings of the transformer core.
A、inductive
B、capacitive
C、resistive
D、reactive
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第12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
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第13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
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第14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
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第15题,Any protection scheme consists basically of ().
A、two elements
B、three elements
C、four elements
D、five elements
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第16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
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第17题,The distance protection is applied to protect ().
A、transformers
B、generators
C、transmission lines
D、buses
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第18题,The thermal energy of the steam is converted into () energy by the turbine.
A、electrical
B、mechanical
C、chemical
D、potential
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第19题,() is used as coolant in light-water reactors.
A、Gas
B、Organic compound
C、Molten salt
D、Water
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第20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
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第21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
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第22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
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第23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
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第24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
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第25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
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第26题,A desktop computer’s sound card sends signals to external ().
A、printer
B、speaker
C、Modem
D、keyboard
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第27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
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第28题,The notebook computers use () as standard display equipment.
A、CRT display
B、LCDs
C、LED
D、TV screen
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第29题,Image clarity on a computer screen is measured with ().
A、screen size
B、dot pitch
C、resolution
D、color depth
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第30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:
第31题,##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## .
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第32题,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 ## .
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