19秋西交《专业英语》在线作业(100分)
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
页:
[1]