联考解剖题库(单选最终版)题目答案搜题软件-威尼斯人最新

时间:2024-06-24 08:16:34


what is applied linguistics in a broad sense?

which of the following is not the feature of applied linguistics?

which of the following is not included in the scope of applied linguistics?

when was the first world congress of applied linguistics held?

in what period of time did the study of applied linguistics develop in china?

generally speaking, applied linguistics means the application of linguistic findings to language teaching and learning.

applied linguistics is inherently interdisciplinary.

the first journal to have the term--applied linguistics in its title was published in edinburgh in 1956.

the establishment of the institute of applied linguistics in 1984 and the publication of “applied linguistics” in 1992 marks the beginning of applied linguistics as an independent discipline in china.

tesol stands for teachers of english to speakers of other languages.

for behaviorists, children learn their first language through ___

the researchers holding an innatist perspective hypothesize that children’s first language learning ability is ___

the best known application of innatist perspective to explain sla is krashen’s ___

when people use the dichotomous terms l1 and l2 in language acquisition research, the ideological root is ____

which theories are proposed from the cognitive perspective in sla research field?

the researchers holding a sociocultural perspective in sla argue that ___.

babies make vowel sounds earlier than consonants.

babies at age two usually understand different word orders would mean different meanings.

babies at three years old usually have developed metalinguistic awareness.

what are the three main perspectives to explain how people acquire their first language?

in sla field, the proponents of linguistic-cognitive sla take ________ as the ideological root while the socioculturally oriented sla researchers prefer ________ as the implied norm.

for the motivation study in sla, please give the major theory/model in the three stages respectively. 1) the first stage, _____________ 2) the second stage, _____________ 3) the third stage, _______________

an extravert does better than an introvert in learning a second language, since such learning requires public performances.

a reflexive learner would consider all the details of a question before he/she gives an answer, while an impulsive learner is likely to be quick in making a response without caring whether it is flawless or not.

field independent learners are likely to be more reflexive than impulsive in learning, and field dependent learners are likely to be the opposite.

motivation and performance are necessarily related positively; i.e. the higher the level of motivation is, the better the performance is, which is always the case.

if a learner learns a second language for the love of it, he/she would learn better than who learns the same language for certain practical purposes.

instrumental motivation for l2 learning may be less long-lasting than integrative motivation, but the former can change into the latter in the course of the learning and usually not vice versa.

high achievers attribute their success to their ability and their failure to chance factors, while low achievers do just the opposite.

serial-position effect shows that in reciting a text, human beings tend to remember very well the beginning and the end of the text, but do poorly the middle parts.

when learners read through a text, they would find that remembering the meaning of the text is no less easy than remembering the structure of the expressions.

doing massed exercises right after a learning task, followed by distributed exercises, is likely to be a desirable pattern of studying, because it is consistent with ebbinghaus retention curve.

phonetics is the science of speech sounds. it studies how the speech sounds are produced, tranitted and perceived. it is language specific.

a phoneme is the allest or minimal contrastive unit which may bring about a change of meaning in a given language.

when two phones are in complementary distribution, they are to be taken as allophones of the same phoneme.

the difference between the initial sounds of chinese (怕) and (爸)is whether it is voiced.

in both chinese and english, /h/ is a voiceless velar fricative consonant.

in communication, what decides which tone to use in a specific context is the sentence pattern

chinese and english differ only in the rhythm pattern.

as the rhythm pattern differs, the prosodic features of the languages concerned differ as well.

in english, the prominence of words with sentence stress is realized by lengthening the accented words only.

imitation is the only and most effective way to learn the pronunciation and intonation of a foreign language well.

speech act excludes:

which is not one of the three major questions required in order to investigate how the learning of l2 is shaped by instructional context and activities?

comparing to correcting pragma-linguistic failure, correcting pragmatic failure stemming from socio-pragmatic miscalculation is a far more delicate matter.

ce & swain (1980) identified pragmatic competence as ( ) competence.

leech (1983) and thomas (1983) ided pragmatics into two components:

bringing pragmatics into the l2 classroom is associated with two main goals:

the notion of pragmatic competence was early on defined by chomsky as the "knowledge of conditions and manner of appropriate use (of the language), in conformity with various purposes".

a speaker's 'linguistic competence' would be made up of pragmatic competence.

taboos is a topic closely related to the concept of 'free' and 'non-free' information.

socio-pragmatics has been described by leech as “the sociological interface of pragmatics,” referring to the social perceptions underlying participants’ interpretation and performance of communicative action.

anthropological linguistics is a sub-field of linguistics which is concerned with the place of language in its wider social and cultural context, its role in forging and sustaining cultural practices and social structures.

linguistic signs as representations of the world and connections to the world are neutral.

linguistic relativi suggested that each language had to be studied in and for itself, and it was not to be forced into a mold that was more appropriate to some other language.

language as cultural resource means that we use language to create a certain culture.

speech as cultural practice means we can find origin, development and future of a certain culture.

chomsky’s notion of performance is connected with “doing things with words.”

participation stresses the inherently social, collective, and distributed quality of any act of speaking.

code switching is not an index.

the same color word can have quite the same associations in different cultures.

if we want to know more about a given society or community by examining the linguistic behavior of its members, we are doing sociolinguistic study of society. that is, we are doing sociolinguistics on a _____ level of investigation.

linguistic variations include:

refers to the phenomenon that those who do not share a first language communicate with each other in a language that they know.

interference of code may happen at the .

sociolinguistics will focus on the studies of the social factors which influence the use of human language.

an inidual must therefore belong to various speech communities at the same time, but on any particular occasion will identify with one of them, the particular identification depending on what is especially important or contrastive in the circumstances.

linguistic differences present greater obstacles to communication than cultural differences do.

code-switching is a phenomenon in a conversation between multilinguals, who alternate from one language to the other out of communicational convenience or preference

and male speakers are heard to use the low-rise intonation with statements much more frequently than female speakers.

in discourse semantics, on the clause level, there is theme and new; on the paragraph level, there is ; on the text level, there is macrotheme and macronew.

context in sfl refers to .

a teaching-learning cycle designed by rothery and her colleagues has several stages, including .

in systemic functional linguistics, there are three contextual variables for context of culture, namely field, tenor and mode.

language has to provide for making links with itself and with features of the situation in which it is used.

discourse ysis interfaces with the ysis of grammar and the ysis of social activity, somewhere at the work of grammarians on the one hand and social theorists on the other.

the initial aim of the sydney school project was to design a reading pedagogy that could enable any student to succeed with the writing demands of the school.

the functional nature of language in systemic functional linguistics is theorized in terms of three meta-functions: ideational, interpersonal and textual.

which of the following statements is not true in the enterprise of cognitive linguistics?

choose the example(s) for instantiating the conceptual metaphor” time is money”.

what are the key claims of cognitive linguistics?

what events officially marked the birth of cognitive linguistics as a broadly grounded, self-conscious intellectual movement?

which of the following descriptions accounts for the different expressions “the cup is half full/the cup is half empty"

cognitive linguistics is a cluster of overlapping approaches to the study of language as a mental phenomenon.

the most important way in which cognitive linguistics differs from other approaches to the study of language, then, is that language is assumed to reflect certain fundamental properties and design features of the human mind.

cognitive linguistics claims that linguistic knowledge is just the grammatical rules and separate from other types of knowledge of our experience of the world.

a conceptual metaphor, also known as a generative metaphor, is a metaphor in which one idea ( or conceptual domain ) is understood in terms of another.

there exists a clear-cut line between categories according to cognitive linguistics.

english is learned as a second language in schools in mainland china.

the grammar-translation method was also called the classical method because it had been used to teach classical languages like latin.

in foreign language classes taught through the direct method, both the students’ mother tongue and the target language are used.

the silent way to foreign language teaching proposes that learners are to discover and create in language learning.

according to community language learning, learning is both cognitive and affective.

according to multiple intelligences model, people’s intelligences exist in many different forms and are stable.

the lexical approach holds that grammar and words are the focus of foreign language learning.

the key elements of communicative competence are linguistic competence, sociolinguistic competence, discourse competence and strategic competence.

content-based instruction in foreign language teaching emphases learning about language instead of learning through language.

in real language teaching practice, both macro planning and micro planning are important.

according to the monitor model, language teachers should provide students with input which is slightly ahead of their current state of language proficiency.

in foreign language learning, output is more concerned with semantic processing than syntactic processing.

in foreign language learning, interaction can aid both the comprehension of input and the production of output.

in foreign language teaching, the only purpose of testing is to assess the students’ achievements in learning.

norm-referenced tests are efficient in selecting students who are qualified for a certain program.

compared to natural science, the tools of measurement of social science are

usually the nature of the collected data of quantitative research is:

what are the characteristics of scientific research?

what are the two essential components of scientific research?

what disciplines could be included in social science?

what are the two basic ways of research in scientific sense?

to differentiate qualitative and quantitative research, we could apply the following criteria:

what are the ways used for collecting quantitative data?

language data is often treated as qualitative data in literatures.

in applied linguistic research we can find three main types of primary data, which are qualitative date, quantitative date, and mixed method data.

primary research is employed by conducting one’s own data-based empirical investigation.

language testing, discourse ysis, conversation ysis, and corpus linguistics are the particular ways to process language data.

there is an absolute boundary between qualitative data and quantitative data.

participant observation means the participant observer becomes a full member of the group, taking part in all the activities.

observers conducting unstructured classroom observation are less clear on what the observation is looking for.

the instructional classroom context deals with the factors of curriculum, power relationship, teaching methods, student identity etc.

research methods in social science: apa format

期末论文选题讨论稿

期末论文选题修改稿

期末proposal

以下说确的是

对一物理量进行等精度多次测量,其算术平均值是

某一物理量的测量值,在进行单位值变换时,其有效数字的位数

以下有效数字计算正确的为( )

以下有效数字计算正确的为( )

根据有效数字的取舍规则,0.0415修约为两位有效数字结果正确的是( )

如果多次测量的平均值为534.274毫米,误差为0.5毫米,测量结果应表示为( )

下述结果表示正确的是( )

按有效数字运算规则,算式48×3.2345/1.73 的值为( )

服从正态分布的随机误差具有下面的一些特性( )

常用的数据处理的方法有()

下列不属于系统误差来源的是( )

以下所列误差属于系统误差的有( )

不确定度在可修正的系统误差修正后,将余下的全部误差按产生原因及计算方法不同分为两类,其中由测量仪器产生的误差分量属于a类分量。

有效数字由可靠数字和一位的可疑数字两部分组成。

凡是可以通过统计方法来计算的不确定度称为b类不确定度。

仪器的最大允差就是指在正确使用仪器的条件下,测量所得结果的最大允许误差。

测量次数较少时,误差的分布就不是正态分布,而是服从一种新的分布形式t分布,也叫学生分布,t分布的曲线与正态分布相似。

有效数字经加减运算后,结果有效数字的末位(可疑数)与参与运算的各数中末位数(可疑数)数量级最大的那一位相同。

乘除运算结果的有效数字与参与运算的各位数中位数最多的那一个数相同。

惠斯通电桥适用于测哪类电阻?

用惠斯登电桥可精确测量的电阻范围是( )欧姆。

惠斯登电桥测量电阻实验中,若计算得rx=1997.8ω,urx=3.82ω,则结果报道为( )ω。

惠斯登电桥实验中,粗调电桥平衡时,对于滑线变阻器和电位器的使用正确的是( )。

惠斯登电桥实验中,细调电桥平衡时,对于滑线变阻器和电位器的使用正确的是 ( )。

搬动检流计时,要将小旋纽转向红色圆点处。

检流计的小旋纽在红色圆点处,可以转动零位调节器调零。

当接有检流计的电路偏离平衡较远时,检流计的“电计”按钮,按下后应立即松开。

惠斯登电桥测量电阻实验中,应用换臂法的目的是消除电桥的不等臂误差。

惠斯登电桥测量电阻实验中,应用换向法的目的是消除电桥的不等臂误差。

如图,惠斯登电桥实验中,当电位器接ab端时,顺时针转动转柄,阻值变 。(填“大”或“小”)

如图,惠斯登电桥实验中,当电位器接bc端时,顺时针转动转柄,阻值变 。(填“大”或“小”)

如图,惠斯登电桥实验中,当电位器接bc端时,逆时针转动转柄,阻值变 。(填“大”或“小”)

如图,惠斯登电桥实验中,当电位器接ab端时,逆时针转动转柄,阻值变 。(填“大”或“小”)

若示波器发生故障而无扫描信号输出时,在y轴加入正弦波信号,示波器将显示:

如图所示,为示波器测量的某正弦信号的波形,若示波器的垂直(y轴)偏转因数为2.00v/,该信号的电压峰峰值是:

用示波器显某待测正弦信号波形,当扫描速率为0.5ms/div时,测得信号波长为4.0div,则信号频率为:

用示波器测定两个正弦信号的相位差,得到李萨如图形如图所示,那么这两个正弦信号的相位差为:

示波器中扫描发生器的作用是产生线性度好、稳定的:

为了在示波器屏幕上获得稳定的波形,扫描电压周期必须与被测电压周期成整数倍关系。

利用传感器,电子示波器可以进行非电量的测量。

用示波器测定两个正弦信号的相位差,得到李萨如图形是二、四象限内的一条直线,那么这两个正弦信号的相位差为0或2π。

示波器中垂直部份“scale”旋钮的功能是调节屏幕上竖直方向上每一大格所代表的电压。

示波器中水平部份“scale” 旋钮的功能是调节屏幕上水平方向上每一大格所代表的时间。

利用李萨如图形可以测定任何信号的频率。

示波器实验中,要观测到李萨如图,须在水平控制部分的menu菜单时选择 x-y 时基模式。

利用示波器观测rc串联电路暂态过程的实验中,使用的信号源是:

rc串联电路实验中,电路参数不变,若将信号源产生的方波信号频率变小时,电路的时间常数将:

下图是rc串联电路实验中的电容充电波形,从图中可以看出:

rc串联电路实验中,用示波器来观测电容的充电过程,若rc电路时间常数比方波周期t小得多时,则将看到的波形是:

rc串联电路实验中,r=1000ω,c=0.01μf,则该电路时间常数τ的值为:

在rc串联电路暂态过程研究的实验中,通过示波器观察临界饱和时的电容器两端的电压信号uc,可知uc电压变化范围为:

rc串联电路实验中,电路充电快慢与电压大小有关,电压越大,充电越快。

rc串联电路实验中,电路充电快慢只和电路本身的参数有关,而与电源电压大小无关。

在rc暂态过程中,固定方波的频率以及电容器的电容值 ,而改变电阻的阻值,当电阻的阻值由小到大变化时,示波器上可依次观测到三种不同的充放电波形: 未饱和波形、临界饱和波形、过饱和波形。

对于rc串联电路,充电过程中电容上电压随时间按指数规律变化。

在采用二次成像法测薄透镜焦距时,假设物与屏之间的距离为d,透镜焦距为f,则必须满足的前提条件是。

透镜焦距测量的实验中,等高共轴调节的意义?

凸透镜焦距测量的实验中,透镜的光轴必须平行于轨道,为什么?

凸透镜成像实验中,采用二次成像法调节等高共轴。

凸透镜成像实验中,凸透镜的光轴与轨道存在夹角,那么物距的测量值大于实际值。

凸透镜成像实验中,采用自准直法测量焦距时,所成的像是正立的。

透镜成像实验中,景深与人眼无关。

辅助透镜法测量凹透镜焦距实验中,所成的像为虚像。

透镜焦距测量实验中,也可以采用扩束的激光作为光源。

透镜焦距测量实验中,也可以采用平面镜作为像屏。

下列曲线中属于二极管伏安特性曲线的是( )。

下列曲线中属于钨丝灯伏安特性曲线的是( )。

给二极管加一个未超过阈值电压的正向电压时,通过二极管的电流特征是( )。

下面哪些元件为非线性元件

下列电流表使用方法叙述正确的是

钨丝灯的冷态电阻大于热态电阻。

钨丝灯显示正温度系数的关系。

二极管具有单向导电性。

用伏安法测得210欧的电阻,电压表的内阻为10千欧,电阻测量值经方法误差(采用外接法)修正之后的阻值是( )欧姆。

二极管电流修正公式,若测量电路总电压表内阻为ω,当电压表读数为0.7000v时,电流表读数为12.30ma,则修正电流为( )ma。

测量钨丝灯的伏安特性曲线时,采用的伏安法是( )。

测量二极管的伏安特性曲线时,采用的伏安法是( )。

手动切换电器为( )。

hh系列刀开关采用储能分合闸方式,主要是为了( )。

按下复合按钮时,( )。

闸刀开关只用于手动控制容量较小、启动不频繁的电动机的直接启动。

按钮开关是一种结构简单,应用广泛的主令电器。

主令电器主要用来 。

按下复合按钮时,( )。

按钮帽上的颜色用于( )。

手动切换电器为( )。

按钮开关是一种结构简单,应用广泛的主令电器。

闸刀开关只用于手动控制容量较小、启动不频繁的电动机的直接启动。

按钮随堂测验

1、按下复合按钮时,( )。

2、按钮帽上的颜色用于( )。

5、按钮在外力解除以后,触点动作后的开闭状态可以保持。

3、主令电器主要用来 。

4、按钮常用于控制电路, 色表示起动, 色表示停止。

刀开关随堂测验

1、 刀开关安装时,手柄要朝上装。

2、刀开关接线时,电源线接在上端,下端接负载。

5、刀开关可以频繁接通和断开电路。

3、刀开关的额定电压应 控制线路的额定电压。

4、刀开关的额定电流应 线路的额定电流。

2、行程开关可以用作电源分断开关。

4、行程开关是无触点开关。

1、机械式行程开关常见的有 和 两种。

3、行程开关又称为 。

5、转换开关一般是通过外力进行操作,外力撤销后触头的开闭状态( )。

2、转换开关也称为组合开关,是刀开关的一种。

3、转换开关不可以用于电源引入开关。

4、转换开关与按钮操作过程一样,都可以通断电路。

1、万能转换开关是 的主令电器。

什么是低压电器?

按钮通常用做( )或( )控制电路的开关。

低压电器按操作方式分为( )和( )。

万能转换开关是( )的主令电器。

刀开关安装时,手柄要向上装。接线时,电源线接在( ),( )接用电器。

低压断路器随堂测验

4、断路器再线路中可以( )。

5、断路器具备有( )保护功能。

1、通常漏电保护器与低压断路器组合构成( )。

2、低压断路器的操纵结构是实现断路器( )的结构。

3、低压断路器又称为( ) 。

2、熔断器在电路中主要作( )保护。

1、熔断器保护电路时与电路并联。

3、熔断器的额定电流小于或等于熔体的额定电流。

4、熔断器内的熔体既是检测部件又是执行部件。

5、确定( )电流是选择熔断器的主要任务。

3、接触器的型号为cj10-160,其额定电流是( )。

4、交流接触器在不同的额定电压下,主触点的额定电流( )。

5、下面( )不是接触器的组成部分。

6、交流接触器的作用是( ) 。

1、交流接触器通电后,如果铁芯吸合受阻,会导致线圈烧毁。

2、接触器的额定电压是指( )正常工作的电压值。

继电器随堂测验

1、时间继电器的作用是( )。

2、热继电器的整定值为6.8a,则动作范围应选用( )。

3、电磁机构中衔铁可靠地被吸住的条件是( )。

4、关于电压继电器,下列说确的是( )。

5、继电器在任何电路中均可代替接触器使用。

信号灯随堂测验

1、信号灯是用来( )。

2、信号灯一般有( )、灯罩、( )和外壳组成。

判断:热继电器和过电流继电器在起过载保护作用时可相互替代。

下列元件中,常用作位置控制的电器有 。 a、转换开关 b、接触器 c、行程开关 d、时间继电器

下列元件中,主令电器有 。 a、熔断器 b、按钮 c、刀开关 d、速度继电器

熔断器的作用是 。 a、控制行程 b、控制速度 c、短路或严重过载 d、弱磁保护

交流接触器在电路中的主要作用是 。 a、频繁通断主回路 b、频繁通断控制回路 c、保护主回路 d、保护控制回路

5、能用来表示电机控制电路中电气元件实际安装位置的是 b 。 a、 b、 c、 d、

2、电气原理图绘制中,不反映电器元件的大小。

2、电气接线图中,同一电器元件的各部分不必画在一起。

3、在原理图中,各电器元件必须画出实际的外形图。

4、电气原理图中所有电器的触电都按没有通电或没有外力作用时的开闭状态画出。

1、辅助线路包括( )等电路。

1、分析电气原理图正确的方法是( )。

2、分析电路结构一般是( )。

3、识读电气原理图的步骤首先是看( )。

4、分析控制电路最基本的方法是( )。

判断:电气原理图中所有电器的触点都按通电或有外力作用时的开闭状态画出。

判断:电器元件布置图中,强电部分和弱电部分要分开,且弱电部分要加屏蔽,防止干扰。

选择:接触器的型号为cj10-160,其额定电流是 。 a、10a b、160a c、10~160a d、大于160a

选择:欲使接触器km1动作后,接触器km2才能动作,需要 。 a、在km1的线圈回路中串入km2的常开触点 b、在km1的线圈回路中串入km2的常闭触点 c、在km2的线圈回路中串入km1的常开触点 d、在km2的线圈回路中串入km1的常闭触点

选择: 是用来表示电路中各电气元器件导电部件的连接关系和工作原理。 a、电气原理图 b、电气安装接线图 c、电器布置图 d、控制线路图

1、点动控制主要用作生产设备的( )。

2、长动控制是实现设备的( )运转。

3、( )是电动机连续运转的基本控制控制方式。

4、电气系统中的相互制约或禁止的控制是( )控制方式。

判断:电气安装接线图中电器元件的图形符号应与电气原理图标注不相同。

多项选择题: 电气控制系统图分为( )三类。 a、电气原理图 b、 电器元件布置图 c、电气安装接线图 d、电气元器件表图

判断题:电气原理图设计中,应尽量减少电源的种类。

单项选择题: 分析电气控制原理时应当 。 a、先机后电 b、先电后机 c、先辅后主 d、化零为整

单项选择题: 在控制电路中,如果两个常开触点串联,则它们的逻辑关系是 。 a、与逻辑关系 b、或逻辑关系 c、非逻辑关系 d、与非逻辑关系

1、容量大于10kw的笼型异步电机,一般采用全电压直接起动。

2、三相异步电动机常用的电气起动方法有( )和( ) 。

2、11kw以上的笼型电机,进行起动时应采取( )。

3、全压控制,主回路的供电电压一定是380v。

1、( )开关通常用做点动控制电路的主令电器。

判断:全压控制电路中,主回路电压一定是380v。

选择:全压起动一定含有 。 a、电源引入开关 b、起动按钮 c、接触器 d、熔断器

判断:在点动电路中主电路一定要接热继电器。

判断:“自锁控制”就是利用输出信号本身来保持输出动作,又称“自保持环节”。

选择: 如图所示的控制电路可以实现 控制。 a、三相异步电动机的正反控制 b、三相异步电动机的点动控制 c、三相异步电动机的长动控制 d、三相异步电动机的点-长动控制

1、电机正反转运行中的两接触器必须实现相互间 ( ) 。

2、欲使接触器km1和接触器km2实现互锁控制,需要( )。

3、三相异步电动机要想实现正反转( )。

4、电动机正反转控制电路为了保证起动和运行的安全性,要采取电气上的互自锁控制。

1、在正反转电路中,用复合按钮能够保证实现可靠联锁。

4、在点动电路、正反转可逆控制电路中,主电路一定要接热继电器。

2、改变三相异步电动机旋转方向的方法是( ) 。

3、自锁电路是利用( )来保持输出动作,又称“自保持环节”。

1、在控制电路中,如果两个常开触点并联,则它们是( )。

2、自动往返控制电路中的位置限制采用( )开关。

4、改变三相异步电动机转向的方法是( )。

5、用于频繁地接通和分断交流主电路和大容量控制电路的低压电器是( )。

3、只要采取电气上的互锁控制,电动机正反转控制电路就可以实现起动和运行的安全、便捷。

选择: 若接触器用按钮起动,且起动按扭两端并联接触器的常开触点,则电路具有 。 a、零压保护功能 b、短路保护功能 c、过载保护功能 d、弱磁保护功能

选择: 改变交流电动机的运转方向,调整电源采取的方法是 。 a、调整其中两相的相序 b、调整三相的相序 c、定子串电阻 d、转子串电阻

选择: 在控制电路中,如果两个常开触点并联,则它们的逻辑关系是 。 a、与逻辑关系 b、或逻辑关系 c、非逻辑关系 d、与非逻辑关系

电动机正反转控制电路为了保证起动和运行的安全性,要采取电气上的互锁控制。

选择: 如图所示的控制电路可以实现 控制。 a、三相异步电动机的正、停、反控制 b、三相异步电动机的正、反、停控制 c、三相异步电动机的正反转控制 d、三相异步电动机的点长动控制

1、欲使接触器km1动作后接触器km2才能动作,需要( ) 。

2、欲使接触器km1和接触器km2同时动作,需要( )。

1、欲使接触器km1断电返回后接触器km2才能断电返回,需要( )。

2、欲使km2通电工作后才能使km1通电工作,需要在km1的线圈回路串接km2的常开触点。

2、欲km1通电工作后km2才能启动,而接触器km1断电停止后km2才能断电停止,需要( ) 。

1、电压等级相同的两个电压继电器在线路中要同时通电工作,可以直接串接。

电磁机构中衔铁可靠地被吸住的条件是 。

三相异步电动机在运行时出现一相电源断电,对电动机带来的影响主要是 。

欲使接触器km1动作后接触器km2才能动作,需要 。

欲使接触器km1和接触器km2同时动作,需要 。

电动机长动线路装接完成后,按下启动按钮,用万用表测得控制电路的供电电源两端的电阻是0ω,说明 。

电动机长动线路装接完成后,按下启动按钮,电动机启动运行,松开启动按钮后电动机停止,说明 。

下边控制电路可实现 。

下图控制电路可实现 。

电动机点动线路装接完成后,不需要按下启动按钮,只要合上电源开关,电动机就启动运行,说明 。

欲使接触器km1断电返回后接触器km2才能断电返回,需要 。

热继电器在电路中可以实现电路的过载保护。但是电动机起动时电流也很大,热继电器却不会动作,其原因是 。

正在运行的三相异步电动机突然一相断路,电动机会停下来。

在正反转电路中,用复合按钮能够保证实现可靠联锁。

热继电器和过电流继电器在起过载保护作用时可相互替代。

接触器按主触点通过电流的种类分为直流和交流两种。

在点动电路、可逆旋转电路等电路中主电路一定要接热继电器。

电动机的额定转速越高越好。

在电力拖动系统中应用最广泛的保护元件是双金属片式热继电器。

常用的具有短路保护功能的低压电器有:低压断路器和熔断器。

接触器的额定电流是指主触头的额定电流。

判断: 如图所示电路是自锁电路,可以利用输出信号本身自锁来保持输出的动作。

单项选择: 如图所示电路可以实现 控制。 a、点动 b、长动 c、 点动-长动 d、正反转

单项选择: 如图所示电路可以实现 控制。 a、正-反-停 b、 正-停-反 c、自动往返 d、顺序

单项选择题: 电动机控制系统常用的保护环节有 。 a、过载保护 b、失压保护 c、 短路辩护 d、以上都有

光纤的结构主要包括

按照光纤传导模式区分,光纤可以分为多芯和单芯的

现代光纤通信系统中光纤的主要材质是?

光纤中心部分叫

光通信与光纤通信的含义一样吗?

早期光通信与现代意义的光纤通信最主要的区别主要是什么?

2009年,高琨因为光纤通信理论上的巨大贡献,获得了哪一项诺贝尔奖?

1970年代,光纤通信面临实用化挑战,关键技术问题是哪一个?

按照光纤通信系统所使用的传输频段(信号波长)进行分类,以下哪一个不属于光纤通信系统?

现代光纤通信系统中光发射机使用内调制比外调制的速率高。

现代光纤通信系统中,光纤主要是由二氧化硅制成的。

纤芯半径越小,光纤当中的高阶模数量就越少

实现单模传输的条件是v>2.40483

光纤中的色散增大最终会导致传输系统的带宽减小

光隔离器的插入损耗越小越好

光环型器这种器件其端口是互易性的

光隔离器是一种 的器件。

掺铒光纤放大器是属于光-光的放大。

在现在代光纤通信系统中的密集波分复用技术中利用“光-电-光”的放大形式其实也是可以实现的

电子从高能级自发跃迁到低能级也可以放出光,但是这种光不是主要的光放大。

在光信号放大的过程中,edfa的放置形式通常有 , , 三种形式。

led在正常发光时输入电流必须大于阈值流。

led适用于短距离低容量传输,ld适用于长距离大容量传输。

随着温度的升高,ld的阈值电流反而会变低。

20日) 水彩写生——静物

蔬果类,器皿类,花卉类各完成一张水彩静物写生作业,16开以上大小,单个物体或组合都可以,实在感觉不会画的临摹也行。

11日):写生范画

写生或创作性都可以,注意水彩的特性,不可过于简单,实在觉得有难度的可以临摹一张比较优秀的作品。

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