【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
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相关试题
【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
【单选题】
30在以下三种电路中输出电阻最小的电路是___；
A. 共基放大电路
B. 共集放大电路
C. 共射放大电路
【单选题】
当PNP型晶体管工作在放大区时，各极电位关系为uC ___uB。
【单选题】
32当PNP型晶体管工作在放大区时，各极电位关系为uB___uE 。
【单选题】
33测得NPN型三极管上各电极对地电位分别为，，，说明此三极管处在___。
A. 放大区
B. 饱和区
C. 截止区
D. 反向击穿区
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【单选题】
- Will you join us for lunch?____.
A. No, I won't
B. Yes, with pleasure
C. Yes, please
D. Yes, help yourself
【单选题】
- Thank you for your great dinner. I really enjoyed it._____you enjoyed it.
A. I'm so glad
B. I'm sorry
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A. It doesn't matter
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- How was your journey to Paris? - ____
A. It went very well.
B. I flew there.
C. I love Paris.
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- I'm sorry for being late, Mr Lt______.
A. All right
B. That's right
C. Not at all
D. Never mind
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- Happy birthday to you! ___!
A. Happy birthday to you
B. I'm very glad
C. That's all right
D. Thank you
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- Do you like country music?___.
A. Yes, I like basketball a lot
B. It's far too crowded
C. Yes, I'm crazy about it
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- Have a cup of tea, ____? Thanks a lot.
A. don't you
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C. shall we
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【单选题】
- Thank God．It's Friday again．A nice weekend!___.
A. Me too
B. Yes，I'll be free then
C. That's all right
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【单选题】
— Write to me when you get home. OK, I ______.
A. must
B. should
C. will
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【单选题】
Tom is so talkative. I’m sure you'll soon get tired ___ him.
A. of
B. with
C. at
D. on
【单选题】
I don't know ____ to deal with such matter.
A. what
B. how
C. which
D. /
【单选题】
___ is your girl friend like? She is very kind and good-looking.
A. How
B. What
C. Which
D. Who
【单选题】
He ___ driving me home, even though I told him I lived nearby.
A. insisted on
B. insisted at
C. insisted that
D. insisted in
【单选题】
We came finally ___the conclusion that she has been telling lies all the time.
A. of
B. into
C. to
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【单选题】
I won’t make the___mistake next time.
A. like
B. same
C. near
D. similar
【单选题】
He ___lives in the house where he was born.
A. already
B. yet
C. still
D. ever
【单选题】
I am not used to speaking ___ public.
【单选题】
I didn’t know what to do, but then an idea suddenly ___to me.
A. appeared
B. happened
C. occurred
D. emerged
【单选题】
Measles （麻疹） ___ a long time to get over.
A. spend
B. spends
C. take
D. takes
【单选题】
A pair of spectacles ___ what I need at the moment.
A. is
B. are
C. has
D. have
【单选题】
— Five days ___ too long for me to wait.
A. was
B. were
C. is
D. are
【单选题】
You had better ___ a doctor as soon as possible.
A. seeing
B. saw
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【单选题】
The boy is not happy at the new school. He has ___ friends there.
A. few
B. a few
C. little
D. a little
【单选题】
I fell and hurt myself while I ___ basketball yesterday.
A. was playing
B. am playing
C. play
D. played
【单选题】
Tom ___ more than twenty pounds on the novel.
A. spent
B. paid
C. cost
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【单选题】
Don't forget ____ the window before leaving the room.
A. to have closed
B. to close
C. having closed
D. closing
【单选题】
Twenty people were___ wounded in the air crash.
A. quickly
B. wrongly
C. bitterly
D. seriously
【单选题】
The top of the Great Wall is ___ for five horses to go side by side.
A. wide
B. so wide
C. wide enough
D. enough wide
【单选题】
We’ve missed the last bus. I'm afraid we have no ___but to take a taxi.
A. way
B. choice
C. possibility
D. selection
【单选题】
Nancy is considered to be ____ the other students in her class.
A. less intelligent
B. the most intelligent
C. intelligent as well
D. as intelligent as
【单选题】
It's _____ that he was wrong.
A. clearly
B. clarity
C. clear
D. clearing
【单选题】
There ____ a book and some magazines on the desk.
A. is
B. be
C. have
D. has
【单选题】
She is not only my classmate _____ also my good friend.
A. or
B. but
C. and
D. too
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He asked the waiter ___ the bill.
A. on
B. of
C. for
D. after
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_____ you are leaving tomorrow, we can have dinner together tonight.
A. Since
B. While
C. For
D. Before
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I would like to do the job ___ you don't force me to study.
A. in case
B. although
C. though
D. as long as
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The reason I did not go abroad was ___ a job in my home town.
A. because
B. due to
C. that I got
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_____ she survived the accident is miracle.
A. What
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C. As
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