2019秋西交《专业英语》在线作业1（100分）

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【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
正确资料:


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?
正确资料:


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
正确资料:


第4题,ON-OFF information can be represented by (  ) signal.
A、a digital
B、an analog
C、a discrete
D、a control
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


第8题,The electric machine that operates at speeds above synchronous speed works in (  ) region.
A、motoring
B、generating
C、plugging
D、stopping
正确资料:


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
正确资料:


第10题,The primary winding is connected to (  ).
A、the power source
B、the load
C、the measurement instrument
D、the motor
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


第15题,Any protection scheme consists basically of (  ).
A、two elements
B、three elements
C、four elements
D、five elements
正确资料:


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
正确资料:


第17题,The distance protection is applied to protect (  ).
A、transformers
B、generators
C、transmission lines
D、buses
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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
正确资料:


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）
正确资料:


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## .
正确资料:


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 ## .
正确资料: