of a linear time-invariant system.
A. the stability B. magnitude of the steady-state error C. the controllability D. the observability
79. 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
80. 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 81. Any protection scheme consists basically of _____. A. two elements B. three elements C. four elements D. five elements
82. 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 83. The distance protection is applied to protect _____. A. transformers B. generators C. transmission lines D. buses
84. The notebook computers use _____ as standard display equipment. A. CRT display B. LCDs C. LED D. TV screen
85. Image clarity on a computer screen is measured with _____.
A. screen size B. dot pitch C. resolution D. color depth 86. _____ 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） 87. 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
88. 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 89. A desktop computer’s sound card sends signals to external _____. A. printer B. speaker C. Modem D. keyboard
90. 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
五. 将下列短文翻译为中文。
1. Although the direct current is useful, it has one great disadvantage, that is, there is no easy, economical way to increase or decrease its voltage. The alternating current has not this disadvantage. Using a special device, it is possible to transform a high voltage into a low voltage or a low voltage into a high voltage. The device that we use to transform the voltage is called a transformer. The alternating current can also be changed easily into the direct current. The device which can do this is spoken of as a rectifier.
2. Noise is probably the only topic in electronics and telecommunication with which everyone must be familiar, no matter what his or her specialization. It is ever present, and limits the performance of virtually every system. Also, the measurement of it is very contentious, with almost everybody having a different pet method of quantifying it and its effects.
3. The coil to which the voltage is applied is known as the primary, while the one from which the induced voltage is obtained is known as the secondary. If the secondary has more turns than the primary, the transformer is called a step-up transformer in which the AC voltage of the secondary winding is higher than that applied to the primary winding. If the secondary has fewer turns than the primary, the transformer is called a step-down transformer in which the AC voltage of the secondary winding is lower than that applied to the primary winding. In a well-built transformer the product of the secondary voltage multiplied by the secondary current is almost equal to the product of the primary voltage times the primary current.
4. Noise is probably the only topic in electronics and telecommunication with which everyone must be familiar, no matter what his or her specialization. It is ever present, and limits the performance of virtually every system. Also, the measurement of it is very contentious, with almost everybody having a different pet method of quantifying it and its effects.
5. There are two kinds of current: direct current (DC) and alternating current (AC). A direct current is a current flowing in a conductor always in one direction. An alternating current is a current periodically changing its direction of flow. The electric current transmitted through electric power lines is alternating current. This is because AC is easy to control and more economical when we transmit it over long distances. 6. By an electric circuit or network we mean a collection of electrical devices (for example, voltage and current sources, resistors, inductors, capacitors, transformers, amplifiers, and transistors) that are
interconnected in some manner. The various uses of such circuits, though important, is not the major concern of this text. Instead, our prime interest will be with the process of determining the behavior of a given circuit---- which is referred to as analysis.
六. 将下列句子翻译为英文。
1. 同性电荷相斥，异性电荷相吸。 2. 电力可通过远距离传输到用户。 3. 如果开关接通，电流就流过线路。 4. 通常用字母E表示电动势。 5. 电磁波传播的速度和光一样。 6. 我们将大规模发展电力工业。 7. 这台发动机一直运转良好。
8. 电流在电路中流动的速度是非常快的。
9. 如果使用变压器，低电压的电力就能转换成高电压的电力。 10. 这一现象我们称之为电磁感应。 11. 我们把这些物质称为导体。
12. 有两种不同的电荷：正电荷和负电荷。 13. 电流会使导线发热。 14. 电使得收音机工作。
15. 铜允许电流容易地流过它。
答案
一.
1. insulator 2. conductor 3. ampere 4. magnetic 5. millivolt 6. decimal 7. motor 8. disturbance 9. microprocessor 10.program
11. wattage 12. alternator (A.C. generator) 13. in series 14. in parallel 15. Ampere 16. switch 1 7. lamp 18. insulator 1 9. binary 20. Ohm 21. decimal 22. motor 23. disturbance 24. microprocessor 25.program 26. insulator 27. conductor 28. ampere 29. magnetic 30. millivolt 二.
1. T 2. F 3. T 4. F 5. F 6. T 7. F 8. T 9. T 10. F 11. F 12. F 13. F 14. T 15. F 16. F 17. T 18. F 19. T 20. F 21. T 22. F 23. T 24. T 25. T 26. F 27. T 28. F 29. F 30. F 三.
1. energy converter 2. 负载电阻 3. ideal voltage source 4. 内阻 5. rotor 6. 半导体 7. operational amplifier
8. 分布绕组 9. synchronous generators 10. 无功补偿器
11. 额定电枢电流 1 2. ideal source 13. 电路参数 14. periodic current 15. 负反馈 16. direct axis 17. active current component 18. 无功电流分量 19. power networks 20. 数字继电器
21. operational amplifier 22. 分布绕组 23. synchronous generators 24. 无功补偿器 25. energy converter 26. 负载电阻
27. ideal voltage source 28. 内阻 29. rotor 30. 半导体 四.
1. A 2. C 3. A 4. A 5. C 6. C 7. D 8. B 9. B 10. A 11. C 12. A 13. C 14. A 15. A 16. B 17. C 18. B 19. D 20. A
21. B 22. A 23. B 24. C 25. C 26. B 27. B 28. B 29. B 30. D
31. A 32. C 33. A 34. A 35. C 36. A 37. C 38. D 39. D 40. D 41. B 42. D 43. B 44. B 45. C 46. A 47. B 48. C 49. C 50. A 51. C 52. B 53. C 54. B 55. A 56. C 57. B 58. B 59. A 60. B 61. A 62. A 63. A 64. C 65. B 66. A 67. C 68. A 69. C 70. C 71. C 72. D 73. B 74. B 75. D 76. A 77. B 18. A 79. B 80. A 81. A 82. B 83. C 84. B 85. B 86. D 87. C 88. C 89. B 90. B 五.
1. 虽然直流电是有用的，但它有一个突出的缺点，也就是没有简单而经济的方法来提高或降低它的电压。而交流电则没有这一缺点。如果使用一种专门的设备，我们就能够把高压变成低压或把低压变成高压。我们用来改变电压的这种设备叫做变压器。交流电也能容易地被改变成直流电。能够做到这一点的器件就称为整流器。
2. 噪声也许是电子学和电讯工程中每个人必须熟悉的唯一论题，而不管其专业是什么。噪声总是存在的，它限制了事实上每个系统的性能。同时，对噪声的测量是十分有争议的，几乎每个人都有一种对噪声及其效应进行量化的不同的最得意的方法。
3. 外加有电压的线圈被称为初级，而从中获得感应电压的线圈被称为次级。如果次级的匝数比初级多，则变压器就称为升压变压器，在这种变压器中次级绕组的交变电压高于加给
初级绕组的电压。如果次级的匝数少于初级，则变压器称为降压变压器，在这种变压器中，次级绕组的交变电压低于加给初级绕组的电压。在绕制得很好的变压器中，次级电压乘以次级电流的乘积几乎等于初级电压乘以初级电流的乘积。
4. 噪声也许是电子学和电讯工程中每个人必须熟悉的唯一论题，而不管其专业是什么。噪声总是存在的，它限制了事实上每个系统的性能。同时，对噪声的测量是十分有争议的，几乎每个人都有一种对噪声及其效应进行量化的不同的最得意的方法。
5. 电流有两种：一种是直流电（DC），一种是交流电（AC）。直流电是在导体中总是朝一个方向流动的电流。交流电则是周期性地改变其流动方向的一种电流。通过输电线输送的是电流是交流电，这是因为交流电易于控制，且当我们把它输送到远方时比较经济。 6. 所谓电路或网络，我们指的是一堆按某种方式相互连接在一起的电器件（例如电压源和电流源、电阻器、电感器、电容器、变压器、放大器和晶体管）。这种电路的各种用途虽然重要，但并不是本书主要关心的事。而我们的主要兴趣将是在确定某一特定电路的性能这一过程（这称为“分析”）方面。 六.
1. Like charges repel, unlike charges attract.
2. Electric power can be transmitted over long distance to users. 3. The electric current flows through the circuit with the switch on. 4. The letter E is commonly used for electromotive force. 5. Electromagnetic waves travel as fast as light. 6. We shall develop the electric power industry in a way. 7. The engine has given a constantly good performance. 8. The speed at which current flows in circuit is very great.
9. Using a transformer, power at low voltage can be transformed into power at high voltage. 10. This phenomenon we call electromagnetic induction. 11. We call these substances conductors.
12. There are two different kinds of electric charges: positive charges and negative charges. 13. The current can make the wire hot. 14. Electricity makes a radio play.
15. Copper lets the electric current flow easily through it.