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
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
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
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 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
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 B. Mouse C. Monitor D. hard disk 26. A desktop computer’s sound card sends signals to external _____. A. printer B. speaker C. Modem D. keyboard
27. 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
28. The notebook computers use _____ as standard display equipment. A. CRT display B. LCDs C. LED D. TV screen
29. Image clarity on a computer screen is measured with _____.
A. screen size B. dot pitch C. resolution D. color depth 30. _____ 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）
31. Resistors are _____ elements.
A. passive B. active
C. independent sources D. dependent sources
32. 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?
33. 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 34. ON-OFF information can be represented by _____ signal. A. a digital B. an analog C. a discrete D. a control
35. In North American _____ is adopted as standard frequency in electric power system.
A. 25Hz B. 50Hz C. 60Hz D. 125Hz
36. _____ 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
37. 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
38. A D/A is a device that can convert a digital signal to the equivalent _____.
A. digital form B. numerical form C. binary form D. analog form
39. The precision of ADC ( analog-to-digital conversion ) is determined by _____.
A. its speed B. its gain
C. the accuracy of the reference voltage D. the number of binary bits
40. 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
41. A computer printer is _____ device that produces computer-generated text or graphical images on paper. A. an input B. an output
C. a storage D. a data processing
42. _____ carries data out to speakers and headphones, or back from a microphone.
A. A graphics card B. A modem C. A network card D. A sound card
43. A computer’s microprocessor only understands _____ in binary form. A. high-level languages B. machine language C. human languages D. assembly language 44. Delphi belongs to _____.
A. low-level programming language
B. high-level programming language
C. a programming language connected with the computer hardware behavior D. an assembly language
45. A floppy disk drive is _____ device that reads data from and writes data to floppy disks.
A. an input B. an output
C. a storage D. a data processing
46. In a coal-fired power plant, an electrostatic precipitator is used to remove _____ from the combustion gases.
A. solid particle B. SO2 C. CO D. water vapour
47. In cogeneration（热电联产，热电联供） systems, the overall energy efficiencies are raised by _____.
A. important the combustion process
B. providing thermal energy to the customers C. raising the steam temperature D. reducing SO2 emissions
48. The hydropower is well suited for switching according to _____ command to meet changing power needs.
A. a consumer’s B. a user’s
C. a dispatcher’s D. an operator’s
49. The total transfer function for G1?s? and G2?s?in cascade is _____. A. G1?s? B. G2?s? C. G1?s?G2?s? D. G1?s??G2?s?
50. 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 51. 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
52. A frequency response is a function of the variable _____. A. s B. j? C. D D. t
53. The unit of logarithm of the magnitude of a transfer function is _____.
A. radians per second B. volts C. decibel D. octaves 54. The DC-DC converts _____ input to _____ output. A. direct current, alternating current B. direct current, direct current
C. alternating current, alternating current D. alternating current, alternating current
55. The primary winding is connected to _____.
A. the power source B. the load
C. the measurement instrument D. the motor
56. Copper losses are _____ losses in the primary and secondary windings of the transformer core.
A. inductive B. capacitive C. resistive D. reactive
57. The relation A?A results in _____.
A. null B. identity C. indefinite value D. zero
58. The notebook computers use _____ as standard display equipment. A. CRT display B. LCDs C. LED D. TV screen
59. An expansion slot is a long, narrow socket on the motherboard into which you can plug _____.
A. an expansion card B. a modem
C. a network card D. a sound card
C. Kirchhoff’s Current D. Kirchhoff’s Voltage 60. The transformer is a straightforward application of Faraday’s ______ Law.
A. Ohm’s B. Electromagnetic Induction
C. Kirchhoff’s Current D. Kirchhoff’s Voltage 61. 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 62. ON-OFF information can be represented by _____ signal. A. a digital B. an analog C. a discrete D. a control 63. Resistors are _____ elements.
A. passive B. active
C. independent sources D. dependent sources
64. 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?
65. 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 66. The primary winding is connected to _____.
A. the power source B. the load C. the measurement instrument D. the motor
67. Copper losses are _____ losses in the primary and secondary windings
of the transformer core.
A. inductive B. capacitive C. resistive D. reactive
68. _____ 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
69. 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
70. 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
71. 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
72. 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
73. The electric machine that operates at speeds above synchronous speed works in _____ region.
A. motoring B. generating C. plugging D. stopping
74. The thermal energy of the steam is converted into _____ energy by the turbine.
A. electrical B. mechanical C. chemical D. potential 75. _____ is used as coolant in light-water reactors.
A. Gas B. Organic compound C. Molten salt D. Water
76. 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
77. 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
78. The system’s characteristic equation can be used to determine _____