相关试题
【单选题】
开关接2时，电流表的电流为___。
A. 0A
B. 10A
C. 0.2A
D. 约等于0.2A
【单选题】
开关接1时，电流表中流过的短路电流为___。
A. 0A
B. 0.2A
C. 10A
D. 约等于0.2A
【单选题】
正弦交流电常用的表达方法有___。
A. 解析式表示法
B. 波形图表示法
C. 相量表示法
D. 以上都是
【单选题】
电感两端的电压相位超前电流___。
A. 90°
B. 180°
C. 360°
D. 30°
【单选题】
电容两端的电压相位滞后电流___。
A. 30°
B. 90°
C. 180°
D. 360°
【单选题】
应用戴维南定理求含源二端网络的输入等效电阻是将网络内各电动势___
【单选题】
LC 选频振荡电路，当电路频率等于谐振频率时，电路性质为___。
A. 电阻性
B. 感性
C. 容性
D. 纯电容性
【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
【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
推荐试题
【单选题】
Q4: Which of the following is the disadvantage of long commutes?___
A. Traffic jams .
B. Expensive housing .
C. Poorer life quality .
D. A tiring and boring trip .
【单选题】
Q1: What did Katy like about Jason’s last Halloween party?___
A. She liked playing an interesting game .
B. She enjoyed seeing many of her old friends .
C. She enjoyed wearing her Halloween costume .
D. She liked the decorations in Jason's front yard .
【单选题】
Q2: What is the actual reason that Katy doesn’t want to attend Jason’s party?___
A. None of her friends likes Jason .
B. None of Jason's guests is young .
C. She wants to go to Linda's party ..
D. She went to Jason's party last year .
【单选题】
Q3: What is special about Linda’s party?___
A. The party will last four hours .
B. Six people will attend the party .
C. They will have huge bags of candy .
D. They will play a new game called "GuessWho ".
【单选题】
Q4: What will Katy do to solve her problem?___
A. Go to Jason's party .
B. Go to Linda's party .
C. Attend both Jason's and Linda's parties .
D. Celebrate Halloween with her parents .
【单选题】
Q1: What is special about this year’s Black Friday shopping?___
A. Some stores offered bigger holiday discounts .
B. Some stores provided more choices of nightlife.
C. Some stores made efforts to attract young people .
D. Some stores opened much earlier than they used to .
【单选题】
Q2: Why did some stores open at midnight on Thanksgiving night?___
A. To attract young customers .
B. To beat other stores for sale.
C. To let people sleep late the next day .
D. To keep people stay up for the night .
【单选题】
Q3: How many Black Friday shoppers were reported to go to the shops at midnight this year?___
A. 24 percent .
B. 37 percent .
C. 9.5 percent .
D. 23.5 percent .
【单选题】
Q4: What can we learn about the 15-year-old Jenny?___
A. She and her cousins went back home at midnight .
B. She liked the traditional 4 a.m. Black Friday.
C. She preferred midnight shopping to early morning shopping .
D. She and her cousins got up very early to buy discounted items .
【单选题】
Q1: Why did the woman decide to do a triathlon?___
A. Because she did it in college .
B. Because she wanted to be tough .
C. Because her sister did it and liked it .
D. Because her sister said it was good for her .
【单选题】
Q2: When did the man first do a triathlon?___
A. Last year .
B. In college .
C. Last week .
D. In high school .
【单选题】
Q3: How does the man feel about running?___
A. Boring.
B. Scaring .
C. Exciting .
D. Interesting .
【单选题】
Q4: Why doesn’t the woman like swimming in the triathlon?___
A. Because she fears that a big fish might eat her .
B. Because she fears that she would get lost in lakes .
C. Because she doesn't want to scare away small fishes .
D. Because she doesn't like swimming with many people .
【单选题】
Q1: What is the ratio of positive to negative emotions that can make a person happier?___
A. 1:3.
B. 3 :1.
C. 1 :10 .
D. 10 :1.
【单选题】
Q2: What is the most exciting finding about increasing positive emotions?___
A. It improves relationships .
B. It leads to greater success .
C. It helps develop creativity .
D. It contributes to good health .
【单选题】
Q3: What does the speaker say about negative feelings?___
A. People should turn every negative feeling around .
B. Negative feelings can sometimes have positive effects .
C. Negative feelings often cause people to make mistakes .
D. People should never show negative feelings in public places .
【单选题】
Q4: What is the main idea of the passage?___
A. People should learn to manage their emotions .
B. People should be patient with their negative feelings .
C. People should learn to analyze causes of unhappiness .
D. People should identify as many positive feelings as possible .
【单选题】
Q1: What are the man and woman talking about?___
A. Whether nature is magical and kind .
B. Whether nature is powerful and full of risks .
C. Whether Christopher was well prepared for the trip .
D. Whether Christopher's trip to Alaska was worthwhile .
【单选题】
Q2: What can we learn about Christopher?___
A. He made a film about his trip to Alaska .
B. He wrote a story about his trip to Alaska .
C. He died while having an adventure in Alaska .
D. He learned how powerful and risky Alaska was .
【单选题】
Q3: What does the woman think about Christopher taking the trip to Alaska?___
A. He was too foolish .
B. He was really romantic .
C. He had a very kind heart .
D. He had a spirit for trying things .
【单选题】
Q4: Which of the following is NOT mentioned as something that would have saved Christopher’s life?___
A. A gun to hunt .
B. The map of the area .
C. Emergency food supplies .
D.
E. mergency communication equipment .
【单选题】
Q1: What speed can an avalanche reach within five seconds of taking off?___
A. At 8 miles an hour .
B. At 18 miles an hour .
C. At 80 miles an hour .
D. At 88 miles an hour .
【单选题】
Q2: According to the passage, under what circumstances may an avalanche occur?___
A. There are too many layers of snow on the .
B. There is a layer of snow covering an entire area .
C. The top layer of snow slides off the layer below it .
D. The layer of snow below the surface becomes unstable .
【单选题】
Q3: What are skiers advised to do to avoid being caught in an avalanche?___
A. Ski only in the official ski areas .
B. Look for solid snow to walk on .
C. Look out for each other while skiing .
D. Learn to control themselves in an avalanche .
【单选题】
Q4: Why does the ski patrol use explosives?___
A. To dig holes in the snow .
B. To close the area for skiing .
C. To make an avalanche move on purpose .
D. To' check how different layers are holding up .
【单选题】
Q1:What is conversation mainly about?___
A. The woman's happy college life the man's doubt .
B. The woman's spending habits and the man's concerns .
C. The man's reminding the woman of the exam this Thursday .
D. The man's support for the woman over the past 15 years .
【单选题】
Q2:What did the woman do last night?___
A. She bought a new leather coat .
B. She studied very hard for an exam .
C. She treated all her friends to dinner .
D. She went to a concert with her friends .
【单选题】
Q3:Where did the woman get the money?___
A. She just received her student loan .
B. She saved some money for herself .
C. She borrowed the money from her friends .
D. She asked her mom to send her the money .
【单选题】
Q4:What is the man?___
A. A teacher of biology .
B. An undergraduate student .
C. A freshman in biology class .
D. A graduate teaching assistant .
【单选题】
Q1: What is this passage mainly about?___
A. How businesses can compete with each other .
B. How small businesses operate during holidays .
C. How small businesses manage holiday workers .
D. How can earn more money during holidays .
【单选题】
Q2: According to Rubin, what can small companies do to thank holiday workers?___
A. Have talks with their families .
B. Give them good extra benefits .
C. Offer them expensive holiday tokens .
D. Show appreciation to them face to face .
【单选题】
Q3: What can small business owners do to help holiday workers get into the holiday spirit?___
A. Entertain them with big meals .
B. Let them enjoy some holiday games .
C. Give them handmade thank-you cards .
D. Send their families some holiday gift cards .
【单选题】
Q4: Who are supposed to benefit most from this passage?___
A. Workers who have to work during holidays .
B. Employees who intend to earn extra money .
C. Big companies that usually close on holidays .
D. Small businesses that try to be more competitive .
【单选题】
In the first two paragraphs of the passage the writer tries to tell us that___
A. he had lived in Washington D.C. for twenty years
B. he was very imaginative when he was a child
C. he had fond memories of his old neighborhood
D. )he had come from a very poor neighborhood
【单选题】
The writer ,as a child ,was very fond of playing in the basement because ___
A. it was bright and alive
B. it contained a movie house and a space station
C. it was ideal for playing hide-and-seek
D. it was surrounded by trees and flowers
【单选题】
How did the writer feel when he visited his old neighborhood in Washington D.C. ?___
A. Greatly surprised .
B. Very regretful .
C. Quite excited .
D. Very sad .
【单选题】
On his visit to his hometown ,the writer found the old apartment building___
A. see medunfit to live in
B. had been repaired
C. could hardly be recognized
D. looked dirty and smelt horrible
【单选题】
" Youcan never go home again "inthe last sentence of this passage means that___
A. one should never revisit his hometown after many years of absence
B. one will never find his hometown the same as it was in his childhood memory
C. avisit to one's hometown will bring back one's fond memories of home
D. avisit to one's hometown will bring back many sad memorie
【单选题】
We learn from the passage that Tracy died___
A. on December 8,1992
B. of brain damage
C. 24 hours after he fell off the roof of a car
D. in a car crash
【单选题】
Tracy's parents decided to donate Tracy's organs because___
A. Tracy told them to do so just before he died
B. they wanted to save others the pain of seeing a dear one die
C. David's life could continue in a meaningful way
D. they knew David was suffering from a hopeless liver disease
