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试卷名称:西交《专业英语》在线作业
1.Resistors are ( ) elements.
A.passive
B.active
C.independent sources
D.dependent sources
答案:-
2.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?
答案:-
3.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
答案:-
4.ON-OFF information can be represented by ( ) signal.
A.a digital
B.an analog
C.a discrete
D.a control
答案:-
5.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
答案:-
6.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
答案:-
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.1000
B.900
C.700
D.600
答案:-
8.The electric machine that operates at speeds above synchronous
speed works in ( ) region.
A.motoring
B.generating
C.plugging
D.stopping
答案:-
9.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
答案:-
10.The primary winding is connected to ( ).
A.the power source
B.the load
C.the measurement instrument
D.the motor
答案:-
11.Copper losses are ( ) losses in the primary and secondary
windings of the transformer core.
A.inductive
B.capacitive
C.resistive
D.reactive
答案:-
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
答案:-
13.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
答案:-
14.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
答案:-
15.Any protection scheme consists basically of ( ).
A.two elements
B.three elements
C.four elements
D.five elements
答案:-
16.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
答案:-
17.The distance protection is applied to protect ( ).
A.transformers
B.generators
C.transmission lines
D.buses
答案:-
18.The thermal energy of the steam is converted into ( ) energy by
the turbine.
A.electrical
B.mechanical
C.chemical
D.potential
答案:-
19.( ) is used as coolant in light-water reactors.
A.Gas
B.Organic compound
C.Molten salt
D.Water
答案:-
20.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
答案:-
21.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
答案:-
22.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
答案:-
23.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
答案:-
24.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
答案:-
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 |
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发表于 2019-7-8 14:04:14
