【单选题】
阻值为4Ω的电阻和容抗为3Ω的电容串联，总复数阻抗为___
A. 3+j4
B. 3-j4
C. 4+j3
D. 4-j3
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相关试题
【单选题】
电动势为10V，内阻为2Ω的电压源变换成电流源时，电流源的电流和内阻是___
A. 10A，2Ω
B. 20A，2Ω
C. 5A，2Ω
D. 2A，5Ω
【单选题】
电流为5A，内阻为2Ω的电流源变换成一个电压源时，电压源的电动势和内阻为___
A. 10V，2Ω
B. 2.5V，2Ω
C. 0.4V，2Ω
D. 4V，2Ω
【单选题】
额定电压都为220V的40W、60W、100W三灯泡串联在220V的电源中，它们的发热量由大到小排列为___
A. 100W 60W 40W
B. 40W 60W 100W
C. 100W 40W 60W
D. 60W 100W 40W
【单选题】
在正弦交流电的解析式i=ImSin(ωt +φ)中，φ表示___
A. 频率
B. 相位
C. 初相位
D. 相位差
【单选题】
正弦交流电压u=100Sin(628t + 600)V，它的最大值为___。
A. 100 V
B. 100 V
C. 60V
D. 628 V
【单选题】
能表示容性电路电压与电流关系的相量图是___。
【单选题】
电路中___定律指出：流入任意一节点的电流必定等于流出该节点的电流。
A. 欧姆
B. 基尔霍夫电流
C. 楞次
D. 基尔霍夫电压
【单选题】
已知电源电压为12 V ,四只相同灯泡的工作电压都是6 V，要使灯泡都能正常工作，则灯泡应___
A. 全部串联
B. 两只并联后与另两只串联
C. 两两串联后再并联
D. 全部并联
【单选题】
用戴维南定理分析电路“入端电阻”时，应将内部的电流源___处理。
【单选题】
任何一个含源二端网络都可以用一个适当的理想电压源与一电阻___来代替。
A. 串联
B. 并联
C. 串联或并联
D. 随意联接
【单选题】
用交流电流表测得交流电流10A，则电路中电流的最大值为___。
A. 10A
B. 14.1A
C. 20A
D. 70.7A
【单选题】
如右图所示电路中，已知各支路的电流I1=I2=10A， 则电路的总电流I为___。
A. 20A
B. 0 A
C. 14.1A
D. 50A
【单选题】
1杂质半导体中多数载流子的浓度取决于___
【单选题】
2在电场作用下，空穴与自由电子运动形成的电流方向___
【单选题】
4下列半导体材料哪一种的热敏性突出“导电性受温度影响最大”？___
A. 本征半导体
B. N型半导体质
C. P型半导体
【单选题】
5用万用表电阻挡检测某一个二极管时，发现其正、反电阻均近于1000KΩ，这说明该二极管是属于___。
A. 短路状态；
B. 完好状态；
C. 断路状态；
D. 极性搞错。
【单选题】
6稳压二极管是一个可逆击穿二极管，稳压时工作在___状态。
【单选题】
7三端集成稳压器CW7812的输出电压是___。
【单选题】
8三端集成稳压器CXX7805的输出电压是___
【单选题】
9一个平衡PN结，用导线将P区和N区连起来，而导线中___。
A. 有微弱电流
B. 无电流
C. 有瞬间微弱电流
【单选题】
10二极管两端正向电压大于___电压时，二极管才导通。
【单选题】
11当温度升高时，二极管的反向饱和电流 ___ 。
A. 增大；
B. 减小；
C. 不变；
D. 无法判定。
【单选题】
12硅二极管的正向导通压降比锗二极管的___ 。
【单选题】
13三端集成稳压器 CW7906的输出电压是___
【单选题】
14稳压管的工作是利用伏安特性中的___。
A. 正向特性
B. 反向特性
C. 反向击穿特性
【单选题】
15二极管具有___
A. 正向特性
B. 反向特性
C. 单向导电特性
D. 反向击穿特性
【单选题】
16图中D1-D3为理想二极管，A，B，C灯都相同，试问___灯最亮。
【单选题】
18在单相桥式整流电容滤波电路中，设U2为其输入电压，输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
19在单相桥式整流电路中，设U2为其输入电压，输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
20在半波整流电容滤波电路中，设U2为其输入电压，输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
21在半波整流电路中，设U2为其输入电压，输出电压的平均值约为___。
A. U0=0.45U2
B. U0=1.2U2
C. U0=0.9U2
D. U0=1.4U2
【单选题】
22温度影响了放大电路中的___，从而使静态工作点不稳定。
A. 电阻；
B. 电容；
C. 三极管；
D. 电源。
【单选题】
23用直流电压表测得放大电路中某三极管各极电位分别是2V、6V、2.7V，则三个电极分别是___。
A. [B、C、E]
B. [C、B、E]
C. [E、C、B]
【单选题】
24共射极放大电路的交流输出波形上半周失真时为___
【单选题】
25三极管的反向电流ICBO是由___组成的。
A. 多数载流子
B. 少数载流子
C. 多数载流子和少数载流子
【单选题】
27如果在NPN型三极管放大电路中测得发射结为正向偏置，集电结也为正向偏置，则此管的工作状态为___
A. 放大状态；
B. 截止状态；
C. 饱和状态；
D. 不能确定。
【单选题】
28在以下三种电路中输入电阻最大的电路是___。
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
【单选题】
29在以下三种电路中既能放大电流，又能放大电压的电路是___。
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
推荐试题
【单选题】
13. Her son __________ Coke, but now he __________ milk．
A. is used to drinking; used to drink B. used to drink; uses to drink
C. used to drink; is used to drinking D. is used to drink; is drinking
【单选题】
14. I don’t know the teacher is talking with Miss Wang．
A. what B. whom C. who D. which
【单选题】
15.Millie does __________ that many people are thankful to her．
A. such an important and helpful job B. so important and helpful work
C. a very important and helpful job D. such an important and helpful work
【单选题】
16. I think eating more vegetables is good _______ our health.
—Yes, I agree _______ you.
A. at, to B. for, with C. to, to D. for, to
【单选题】
17. I often go on holiday with my parents _____ summer.
A. in B. at C. on D. of
【单选题】
18. I called you at 4:00 yesterday afternoon, but nobody answered.
Sorry, I ______ with my friends at that time.
A. had swum B. swam C. would swim D. was swimming
【单选题】
19.––Who is on the playground? ---__________．
A. Never B. None C. No one D. A lot
【单选题】
20. The schoolboy ______ a blind man cross the street yesterday.
A. helps B. helped C. will help D. has helped
【单选题】
21. —The 2010 World Expo which will last 184 days will be held in Shanghai on May 1st.
—________exciting news! We shall try our best to support it.
A. How B. How an C. What D. What an
【单选题】
22. They preferred ______ in bed rather than _____ horses．
A. to lie; to ride B. lying; riding C. lying; ride D. to lie; ride
【单选题】
23. —What was Jim wearing at the party?
— Nothing _______. He was in his usual shirt and jeans.
A. special B. simple C. important D. interesting
【单选题】
24. The 2016 Olympic Games ________ in Brazil. Would you like to go there?
Maybe, if possible.
A. are held B. will be held C. were held D. have been held
【单选题】
25. — David, look at the man in white over there．Can you tell me _______ ?
—He is a doctor．
A. who is he B. who he is C．what does he do D. what he does
【单选题】
( ) 26.With help from a Mr. H, you can__________.
A. stop wearing your watch B. get new books and objects
C. finish your homework on time D. know when parents or teachers are near
【单选题】
( ) 27. A PENGO WATCH CONTROL can help you to ______________.
A. repair your TV B. put away your books and objects
C. become a James Bond D. get a daily weather report
【单选题】
( ) 28. You can get your Mr. H for___________.
A. $299 B. $499 C. $199 D. $99
【单选题】
( ) 29. When was canned food invented?
A. In 1870. B. In 1810. C. In 1902. D. In 1926.
【单选题】
( ) 30. After the trip to the Arctic, Clarence Birdseye invented ____________.
A. canned food B. can openers
C. frozen food D. air conditioning
【单选题】
( ) 31. Changes in weather _____________ in Willis Carrier's company.
A. helped to keep food B. made rooms comfortable
C. caused health problems D. hurt printing paper
【单选题】
( ) 32. According to the passage, which of the following may lead to inventions?
A. People's needs. B. Public support.
C. Modern technology. D. Practical suggestions.
【单选题】
( ) 33. What is the writer's main purpose（目的）in writing this passage？
A．To tell the readers his life story．
B．To tell people what kind of person his father was．
C．To tell the readers what present he got from his father．
D． To let people know how poor he was．
【单选题】
( ) 34. Why did the father not ask his son not to do this and do that？
A．Because he felt quite confident of his son．
B．Because he was born from a poor family．
C．Because he was a man of few words．
D．Because he didn't want to be much too strict with his son．
【单选题】
( ) 35. What would someone learn from this passage？
A．How to live by oneself． B．How to stand on one's own feet．
C．What a good father should do． D．What the self-important is like．
【单选题】
( ) 36. What may be the proper Chinese for the underlined part in the passage？
A．闲暇时光 B．学费 C．精神空虚 D．经济不足
【单选题】
( ) 37. The Chinese Yellow Sea Wetlands are in the _______ of China．
A．south B．east C．west D．north
【单选题】
( ) 38. Usually the weather in the wetlands is _______．
A．hot B．pleasant C．cold D．dry
【单选题】
( ) 39. The World Wetlands Day is on _______．
A．February 2 B．June 25 C．April 22 D．March
【单选题】
( ) 40. We must protect wetlands because _______．
A．they are home for wildlife B．they can prevent flood
C．they can offer food to the animals and birds D．all of the above
【单选题】
) 1. —Is it far from here to the bank?
—Not very, only________．
A. 20 minute’s walk B. 20 minutes walk
C. 20 minutes’ walk D. 20 minutes’ walks
【单选题】
2. — After discussing, the students ________ some good ideas to work on the project.
— Thats great!
A. put up B. set up C. caught up with D. came up with
【单选题】
3. Yesterday Tommy walked past my table and ______ my bowls and dishes.
He should be careful next time.
A. knocked off B. took off C. showed off D. turned off
【单选题】
4.We don’t have enough nurses to look after patients．At least ___ nurses are needed．
A. ten another B. more ten C. another ten D. other ten
【单选题】
5. — Zhao Rui, it’s said that many famous singers will come to Yangzhou on April 18th. How about watching the evening show there?
—________! Let’s ask Huang Tao to go with us.
A. Best wishes B. Sounds great C. Good luck D. That’s OK
【单选题】
6.—Hello! This is Henry Speaking．I’d like to speak to your father．
—Sorry, he has Shanghai．
A. been in B. been to C. come to D. gone to
【单选题】
7. — It’s difficult for the village children to cross the river for school．
— I think a bridge ______ over the river．
A. was built B. is being built C. has been built D. should be built
【单选题】
8. —Where would you like to go, Jinan or Qufu?
— ．I only want to go to Qingdao．
A. Each B. Either C. Neither D. All
【单选题】
9 — The documentary A Bite Of China II is quite popular around China recently. How do you like it? ______.
A. I think so B. Pretty good C. Its my pleasure D. All right
【单选题】
10. There are three English-books on the shelf, but ______ of them is mine.
A. both B. neither C.all D. none
【单选题】
11. When the parents arrived at the hall, the students _______ their projects.
A. have finish B. finished C. had finished D. are finishing
【单选题】
12. This week, the _______ seems to change every day: one day is hot; the next day is cold.
A. time B. weather C. season D. way
