2022动力与电气工程冲刺练习

戴维宁定理指出:对外部电路而言,任何一个线性的有源双端网络,都可以等效成()。

  • A、一个理想电压源与电阻串联的形式
  • B、一个理想电压源与电阻并联的形式
  • C、一个理想电流源与电阻并联的形式
  • D、一个理想电流源与电阻串联的形式

正确答案:A

戴维宁定理说明一个线性有源二端网络可等效为()和内阻()连接来表示。


正确答案:开路电压Uoc ;串联

电路如图所示,试用戴维宁定理求解电流I。


参考答案:

戴维宁定理既适用于线性电路,也适用于非线性电路。


正确答案:错误

戴维宁定理可表述为:任何一个线性有源二端网络总可以等效为一个理想电压源和一个电阻相串联的电路。


正确答案:正确

非正弦周期电流电路的分析,利用了线性电路分析中的()。

  • A、戴维宁定理
  • B、诺顿定理
  • C、叠加定理
  • D、特勒根定理

正确答案:C

在戴维宁定理中,等效电源的电动势和内阻分别等于有源二端网络的()。


正确答案:开路电压有源二端网络中的所有电源作零值电源处理后的无源二端网络的等效电阻

戴维宁定理


正确答案:在线性电路中,任何一个含有独立源的二端网络,对外电路而言,可以用一个理想电压源与电阻串联的电路等效代替。电压源的电压等于有源二端网络的开路电压,电阻等于有源二端网络中所有独立电源置零后的等效电阻。

戴维宁定理说明任何一个线性有源二端网络N,都可以用一个等效电压源即N二端子的()和内阻R0串联来代替。


正确答案:开路电压

利用戴维宁定理求题4-16图所示电路中的电流I。


答:

说明戴维宁定理的正确性。计算表3.1的相对误差,并分析误差原因。


正确答案: 根据实验数据可得出结论:戴维宁定理是完全正确的。
实验中所得的误差的原因可能有以下几点:
(1)实验所使用的电压表虽内阻很大,但不可能达到无穷大,电流表虽内阻很小,但不可能为零,所以会产生一定的误差。
(2)读数时的视差。
(3)实验中所使用的元器件的标称值和实际值的误差。
(4)仪器本身的误差。
(5)系统误差。

已知r=3Ω,利用戴维宁定理求题4-23图所示电路中的电流I。


答:

戴维宁定理说明任何一个线性有源二端网络N,都可以用一个等效电压源即N二端子的()电压和()串联来代替。


正确答案:开路;内阻R0

判断题
戴维宁定理既适用于线性电路,也适用于非线性电路。
A

B


正确答案:
解析: 暂无解析

RC一阶电路的分析,主要需要利用戴维宁定理。


正确答案:正确

关于处方管理,下列叙述中错误的是( )


正确答案:C

下列关于麻黄现代应用的叙述,错误的是

A、感冒

B、支气管哮喘

C、低血压状态

D、鼻塞

E、心脏病


参考答案:E

改正下列叙述中的错误。“齐将田忌善而客待之”(《史记·孙子列传》)中,“客”,即“把他当作客人”的意思。


正确答案:客为名词作状语,即把他当作客人一样。

下列关于齐次坐标和坐标系叙述,错误的是( )?

A齐次坐标的引入使基本变换具有统一的表示形式,便于变换合成。

B齐次坐标的引入增加了实现的难度,不适合硬件实现。

C使用局部坐标系简化了图形对象的描述。

D右手坐标系指当拇指与某一坐标轴同向时,四指所指的方向为绕该轴的正的旋转方向。


参考答案B

关于叠加定理的应用,下列叙述中正确的是( )。

A.叠加定理反映了线性电路的特性,即各个激励所产生的响应是互不影响的
B.叠加定理不适用于计算功率,因为功率不是电流或电压的一次函数
C.叠加定理仅适用于线性电路,不适用于非线性电路
D.叠加定理不适用于含受控源的电路

答案:A,B,C
解析:
如果含有受控源,受控源保留在图中,并非叠加定理不适用于含受控源的电路。

下列关于细菌、真菌在实践应用中的叙述,错误的是()

  • A、醋酸菌酿醋
  • B、青霉菌提取青霉素
  • C、乳酸菌制作酸奶
  • D、酵母菌制作泡菜

正确答案:D

用分离变量法直接求解非稳态导热问题时,以下叙述中不正确的有()

  • A、初始条件必须是齐次的
  • B、必须采用常物性假定
  • C、边界条件必须是齐次的
  • D、微分方程必须是齐次的

正确答案:D

利用齐次定理求解题4-2图所示电路中的电流I。


答:

下列关于化脓性感染的叙述中,错误的是 ( )


正确答案:A

利用齐次定理求解题4-1图所示电路中各节点电压和输出与输人之比u0/us


答:

试分别叙述罗尔中值定理和拉格朗日中值定理。若以S(x)记由(a,(a)),(b,(b)),(x,(x)))三点组成的三角形面积,试对S(x)应用罗尔中值定理证明拉格朗日中值定理。


答案:
解析:
罗尔中值定理:若函数(x)满足如下条件: (1)(x)在闭区间[a,b]上连续;
(2)(x)在开区间(a,b)内可导;
(3)(a)=(b),
则在(a,b)内至少存在一点ξ,使得’(ξ)=0。
拉格朗日中值定理:若函数(x)满足如下条件:
(1)(x)在闭区间[a,b]上连续;
(2)(x)在开区间(a,b)内可导,

在xOy面上考虑,记由A(a,(a),0),B(b,(b),0),C(x,(x),0)三点组成的三角形面积S(x),则

单选题
下列关于慢性肺心病应用洋地黄类药物,错误的叙述是()
A

应该先抗感染治疗

B

应用前需纠正缺氧

C

用小剂量的快作用制剂

D

心率70~80次/分为疗效指标

E

心衰纠正即停用


正确答案: C
解析: 暂无解析

下列关于气体在血液中运输的叙述,错误的是( )。

A.
B.
C.
D.
E.

答案:C
解析:

下列关于进程管理的叙述中错误的是 ( )


正确答案:C
Windows和OS/2是多任务操作系统.他们所所含的CreateProcess函数在凋用后几乎能立即返回,以便更多程序可以被启动。内核中含有的分时器允许多道程穿并发运衍。

下列关于Internet的FTP的叙述中。错误的是( )


正确答案:D
为了保证FTP服务器的安全性,几乎所有的匿名FTP服务器都只允许用户从其下载文件,而不允许用户向其上传文件。

He is fond of playing()piano while his brother is interested in listening to()music.

A/;the

B/;/

Cthe;/

Dthe;the


C

24. Grace ____________.

A. does badly in her studies

B. has a wonderful name

C.is short and quiet

D.is good at playing the piano


正确答案:D
24.D【解析】从第三段最后一句可知。

单选题
He is fond of playing()piano while his brother is interested in listening to()music.
A

/;the

B

/;/

C

the;/

D

the;the


正确答案: B
解析: 暂无解析

Piano软件是简易的网规网优软件,功能实用且方便,可通过使用Piano软件进行()操作。

  • A、查看频点配置
  • B、查看邻区关系
  • C、绘制Rxlevel分布图
  • D、开启DTX功能

正确答案:A,B

We have a piano_ l _______on Tuesday.


正确答案:
32. lesson

Mrs.Peters stopped playing the piano when she began to work.She had lived in a very small?flat,and there had been no room for a piano.But when she married,she had a new flat which was?big enough for one.So she decided to get one and her husband agreed and helped her.She saved?some money,and her parents gave her a generous amount of money for her birthday.Then she went?to a shop and said,"I′ll choose whichever piano does not cost too much and fits into my living room."
When she had paid for the piano,the shop assistant asked her if she would like him to get it?tuned(调音)evey few months.Mrs.Peters agreed.
A few months later she heard from the shop that a man was coming to tune the piano at ten that?morning.Now she had not cleaned the house yet,so it was dusty and untidy.Mrs.Peters hated having?even the least amount of dirt,and felt ashamed whenever strange people saw her house like that.So she had to hurry..to clean everything carefully.It meant a lot of effort,and it made her hot and tired,but anyhow,by the time the man arrived,everything was finished.
She opened the door,and the man was standing there with a big dog.!"Good morning,"the man said politely,"Will it disturb you if I bring my dog in,please?I′m blind,and he leads me wherever?I go.

Mrs.Peters had wasted her time getting everything clean as__________

A.the dog would dirty the house
B.the piano tuner could see nothing in the house
C.the dog disturbed Mrs.Peters
D.the piano tuner always took the dog

答案:B
解析:
【考情点拨】推理判断题。【应试指导】文中讲到,彼得斯夫人精心打扫房间,是因为当陌生人来访时,如果房间很脏、很乱,她会感到很难堪的。而当钢琴调音师到来时,她才知道这是一位盲人,根本看不到房间是否干净。

单选题
According to the speaker, how does the price of an electronic keyboard compare with the price of a piano?
A

The electronic instrument is much more expensive.

B

The electronic instrument is slightly more expensive.

C

The piano is slightly more expensive.

D

The piano is much more expensive.


正确答案: D
解析:
事实细节的找寻和判断。题干中的关键词为price,从而定位到录音中的“One of the most important reasons for the great popularity of electronic instruments is, of course, their relatively low price.”,可知电子乐器之所以如此盛行,其中一个主要原因就是其价位相对低廉。由此可推测,与电子钢琴相比,传统钢琴要贵得多。因此选项D为正确答案。
【录音原文】
  We are rapidly nearing the end of this course in history of classical music. We have covered several centuries in a very short time. Much too short to do the music justice, of course, but then this is a survey course. From now until the end of this term, we will be talking about and listening to electronic music. You probably already know that it was in the 1950s that musical computers and synthesizers first appeared in universities. The first commercial synthesizers were sold about this time, too. The sophistication and complexity of these instruments has now increased to the point that they can produce almost any kind of sound. Some alarmists believe these new instruments will bring an end to classical music or that they already have. You know I don’t share this view, though I agree we are in the midst of revolution in instrument design. This, however, is not the first such revolution in musical history and probably not the last one either. Remember we’ve already studied the similar case in the early 19th century when the piano replaced the harpsichord and modem brass and wind instruments came into being. One of the most important reasons for the great popularity of electronic instruments is, of course, their relatively low price. Well, just look at it, only about 400 dollars for a piano. Naturally this has done a lot to increase sales for electronic instruments, expecting them to completely replace acoustic instruments.

My piano playing has improvedsignificantly since I had a new teacher.

A: definitely
B: generally
C:certainly
D: greatly

答案:D
解析:
句意:自从我有了一位新老师之后,我的钢琴演奏提升非常大。画线单词significantly意为“大大地,显著地”。A项definitely意为“明确地,确切地”,B项generally意为“大体上”;C项certainly意为“当然,确定地”;D项greatly意为“非常,大大的”,与画线单词意义相近。故本题选D。

Tom is good at playing()piano.

A. a

B. an

C. the


参考答案:C

It was quite a feat to move that piano by yourself.()


正确答案:对

My piano playing has improved significantly since I had a new teacher.

A: definitely
B: generally
C: certainly
D: greatly

答案:D
解析:
句意:自从我有了一位新老师之后,我的钢琴演奏提升非常大。画线单词significant-ly意为“大大地,显著地”。A项definitely意为“明确地,确切地”;B项generally意为“大体上”;C项certainly意为“当然,确定地”;D项greatly意为“非常,大大的”,与画线单词意义相近。故本题选D。

The girl arranged to have piano lessons at the training centre with her sister ________ she would stay for an hour.

A.where

B.who

C.which

D.what


正确答案:A

I decided to take()piano playing as my hobby.

A、off

B、to

C、in

D、up


正确答案:D
解析:take up:开始从事,拿起

音乐术语中“Piano”用来表示。()

  • A、弱
  • B、钢琴
  • C、乐器

正确答案:A

Lisa did not come for the piano lesson yesterday. She have missed the bus.()

A. would

B. might

C. should

D. ought to


参考答案:B


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