相关试题
【单选题】
三相对称负载三角形连接时,线电压最大值是相电压有效值的___
A. 1;
B. √3;
C. √2;
D. 1/√3。
【单选题】
对称三相电路角接时,线电流比对应的相电流___
A. 同相位;
B. 超前30°;
C. 滞后30°;
D. 滞后120°。
【单选题】
两只阻值相同的电阻串联后其阻值___
A. 为两只电阻阻值的乘积;
B. 等于两个电阻阻值之和;
C. 等于两个电阻阻值之和的二分之一;
D. 等于两个电阻阻值的倒数和。
【单选题】
在感性负载两端并联容性设备是为了___。
A. 增加电源无功功率;
B. 减少负载有功功率;
C. 提高负载功率因数;
D. 提高整个电路的功率因数。
【单选题】
电阻负载并联时功率与电阻关系是___。
A. 因为电流相等,所以功率与电阻成正比;
B. 因为电流相等,所以功率与电阻成反比;
C. 因为电压相等,所以功率与电阻大小成反比;
D. 因为电压相等,所以功率与电阻大小成正比。
【单选题】
三相对称负载星接时,相电压有效值是线电压有效值的___倍。
A. 1;
B. √3;
C. 3;
D. 1/√3。
【单选题】
三相对称负荷星接时,线电压的最大值是相电压有效值的___倍。
A. √3;
B. 1;
C. 1/√3;
D. √3。
【单选题】
在正弦交流纯电容电路中,下列各式,哪个正确___
A. I=UwC;
B. I=u/wc ;
C. I=U/wC;
D. I=U/C。
【单选题】
主变压器重瓦斯动作是由于___造成的。
A. 主变压器两侧断路器跳闸;
B. 220kV套管两相闪络;
C. 主变压器内部高压侧绕组严重匝间短路;
D. 主变压器大盖着火。
【单选题】
交流测量仪表所指示的读数是正弦量的___
A. 有效值;
B. 最大值;
C. 平均值;
D. 瞬时值。
【单选题】
导线通过交流电流时在导线表面的电流密度___
A. 较靠近导线中心密度大;
B. 较靠近导线中心密度小;
C. 与靠近导线中心密度一样;
D. 无法确定。
【单选题】
通电绕组在磁场中的受力用___判断
A. 安培定则;
B. 右手螺旋定则;
C. 右手定则;
D. 左手定则。
【单选题】
绕组内感应电动势的大小与穿过该绕组磁通的变化率成___
A. 正比;
B. 反比;
C. 无比例;
D. 平方比。
【单选题】
感应调压器定子、转子之间___
A. 只有磁联系,没有电联系;
B. 只有电联系,没有磁联系;
C. 即有磁联系,又有电联系;
D. 无联系。
【单选题】
对异步电动机启动的主要要求___
A. 启动电流倍数小,启动转矩倍数大;
B. 启动电流倍数大,启动转矩倍数小;
C. 启动电阻大;启动电压小。
D. 启动电压大,启动电阻小。
【单选题】
断路器均压电容的作用___。
A. 电压分布均匀;
B. 提高恢复电压速度;
C. 提高断路器开断能力;
D. 减小开断电流。
【单选题】
变压器呼吸器作用___。
A. 用以清除吸入空气中的杂质和水分;
B. 用以清除变压器油中的杂质和水分;
C. 用以吸收和净化变压器匝间短路时产生的烟气;
D. 用以清除变压器各种故障时产生的油烟。
【单选题】
变压器上层油温要比中下层油温___。
A. 低;
B. 高;
C. 不变;
D. 在某些情况下进行。
【单选题】
变压器不能使直流变压原因___。
A. 直流大小和方向不随时间变化;
B. 直流大小和方向随时间变化;
C. 直流大小可变化而方向不变;
D. 直流大小不变而方向随时间变化。
【单选题】
变压器油闪点指___。
A. 着火点;
B. 油加热到某一温度油蒸气与空气混合物用火一点就闪火的温度;
C. 油蒸气一点就着的温度;
D. 液体变压器油的燃烧点。
【单选题】
变压器铜损___铁损时最经济。
A. 大于;
B. 小于;
C. 等于;
D. 不一定。
【单选题】
某变压器的一、二次绕组匝数比是25,二次侧电压是400V那么一次侧电压为 ___。
A. 10000V;
B. 35000V;
C. 15000V;
D. 40000V。
【单选题】
在6-10kV中性点不接地系统中,发生接地时,非故障相的相电压将___
A. 不升高;
B. 同时降低;
C. 升高1.732倍;
D. 升高一倍。
【单选题】
电流互感器在运行中必须使___
A. 铁芯及二次绕组牢固接地;
B. 铁芯两点接地;
C. 二次绕组不接地;
D. 铁芯多点接地。
【单选题】
变压器带___负荷时电压最高。
A. 容性;
B. 感性;
C. 阻性;
D. 线性。
【单选题】
在流量补偿中进行的压力、温度修正是修正的___误差.
A. 系统误差;
B. 偶然误差;
C. 疏忽误差;
D. 随加误差
【单选题】
若一台1151压力变送器接线有接地现象,则会___.
A. 电压降低;
B. 电压升高; c.电流降低;
【单选题】
测量稳定压力时,被测介质的最大工作压力不得超过仪表量程的___.
A. 1/2;
B. 1/3;
C. 2/3;
D. 3/5
【单选题】
一台1151压力变送椿量程范围为o~300kPa,现零位正迁50%,则仪表的量程为___。
A. 150kPa;
B. 300kPa;
C. 450kPa;
D. 250kPa
【单选题】
若一台压力变送器在现场使用时发现量程偏小,将变送器量程扩大,而二次显示仪表量程未做修改,则所测压力示值比实际压力值___.
【单选题】
过渡过程品质指标中,余差表示___.
A. 新稳击值与给定值之差;
B. 测量值与给定值之差;
C. 调节参敷与被调参数之差;
D. 超调量与给定值之差
【单选题】
关于调节系统方块图的说法,正确的是___。
A. 一个方块代表一个设备;
B. 方块间的连线代衰的是方块间物料关系;
【单选题】
锅炉燃烧调节中的风量调节一般选用___.
A. 均匀调节系统;
B. 比值调节系统;
C. 前馈调节系统;
D. 三冲量调节系统
【单选题】
在研究动态特性时可以将___看作系统对象环节的输入量.
A. 干扰作用;
B. 控制起作用;
C. 干扰作用和控制作用;
D. 测量仪表辖信号
【单选题】
正确选择压缩机防喘振调节阀作用形式是___.
A. 阀前式;
B. 气开式;
C. 气关式;
D. 阀后式
【单选题】
我国生产的单、双座调节阀,R值一般为___.
【单选题】
___是采用扫描方式工作的.
A. 可编程序控制器;
B. 工控机;
C. 普通PC机;
D. 单片机
【单选题】
对于西门子PLC,FB表示的是___.
A. 功能块;
B. 组织块;
C. 功能调用;
D. 数据块
【单选题】
油压千斤顶在使用的过程中只允许使用的方向是___。
A. 水平;
B. 垂直;
C. 倾斜;
D. 任意方向
【单选题】
特殊工序是指___
A. 需要有特殊技巧或工艺的工序;
B. 有特殊质量要求的工序;
C. 加工质量不能通过其后产品验证和试验确定的工序;
D. 关键工序
推荐试题
【单选题】
The main duty of the British Privy Council is to .
A. A. make decisions
B. B. give advice
C. C. pass bills
D. D. supervise the Cabinet
【单选题】
is the first African-American winner of the Nobel Prize for Literature.
A. A.Ralph Ellison
B. B. Tony Morrison
C. C. Richard Wright
D. D. James Baldwin
【单选题】
Of the following writers, is Not a Nobel Prize winner.
A. A. Alice Walker
B. B. Ernest Hemingway
C. C. William Faulkner
D. D. Eugene O’Neil
【单选题】
Of the following books, is NOT written by Ernest Hemingway.
A. A. The Sun Also Rises
B. B. The Sound and the Fury
C. C. A Farewell to Arms
D. D. For Whom the Bell Tolls
【单选题】
F. Scott Fitzgerald’s finest novel is , and its theme is about
A. A. The Great Gatsby, the American Dream
B. B. Tender is the Night, love
C. C. Tales of the Jazz Age, the loss of oneself
D. D. The Beautiful and the Damned, the evil of human nature
【单选题】
Of the following writers, is NOT included in the group of naturalists.
A. A. Stephen Crane
B. B. Frank Norris
C. C. Theodore Dreiser
D. D. Herman Melville
【单选题】
Of the following, is NOT characteristic of Mark Twain’s works.
A. A. colloquial speech
B. B. a sense of humor
C. C. a realistic view
D. D. an idealistic view
【单选题】
Of the following, is considered Herman Melville’s masterpiece.
A. A. The Last of the Mohicans
B. B. The Legend of Sleepy Hollow
C. C. Moby Dick
D. D. Daisy Miller
【单选题】
Of the following, is NOT Nathaniel Hawthorne’s work.
A. A. The Scarlet Letter
B. B. The House of the Seven Gables
C. C. The Marble Faun
D. D. Nature
【单选题】
is regarded as “the father of American literature”.
A. A. James Fennimore Cooper
B. B. Ralph Waldo
C. C. Thomas Jefferson
D. D. Washington Irving
【单选题】
Of the following writers, are from the Colonial and Revolutionary Periods.
A. A. Benjamin Franklin & Edgar Ellen Poe
B. B. Edgar Ellen Poe & Jonathan Edwards
C. C. Benjamin Franklin & Jonathan Edwards
D. D. Edgar Ellen Poe & Washington Irving
【单选题】
The National Day of the United States falls on .
A. A. June 4th
B. B. July 4th
C. C. June 14th
D. D. July 14th
【单选题】
Of the following, is NOT among the three major radio and TV networks in America.
A. A. the National Broadcasting System (NBS)
B. B. the Public Broadcasting Service (PBS)
C. C. the Columbia Broadcasting System (CBS)
D. D. the American Broadcasting System (ABS)
【单选题】
is sold especially to the upper or upper-middle class and it has a reputation for its serious attitude and great bulk.
A. A. The Washington Post
B. B. The New York Times
C. C. Los Angeles Times
D. D. New York Daily News
【单选题】
Of the following universities, has NOT cultivated any American President yet.
A. A. Harvard University
B. B. Massachusetts Institute of Technology
C. C. Princeton University
D. D. Yale University
【单选题】
To get a bachelor’s degree, all undergraduate students are required to do the following except .
A. A. attending lectures and completing assignments
B. B. passing examinations
C. C. working for communities
D. D. earning a certain number of credits
【单选题】
Of the following, is NOT the responsibility of the board of trustees in U. S. institutions.
A. A. choosing the president
B. B. establishing policies for administrators and faculty
C. C. approving budget and other financial project
D. D. decide which student to enroll
【单选题】
Of the following, are NOT among the categories of American higher education.
A. A. universities and colleges
B. B. research institutions
C. C. technical institutions
D. D. community colleges
【单选题】
Higher education in the United States began with the founding of
A. A. Yale University
B. B. Harvard University
C. C. Princeton University
D. D. New York University
【单选题】
Of the following subjects, are NOT offered to elementary school students.
A. A. mathematics and languages
B. B. politics and business education
C. C. science and social studies
D. D. music and physical education
【单选题】
Formal education in the United States consists of , secondary and higher education.
A. A. kindergarten
B. B. public
C. C. elementary
D. D. private
【单选题】
At present, U. S. exports account for of the world’s total.
A. A. 10%
B. B. 15%
C. C. 20%
D. D. 25%
【单选题】
is not one of the three giants in American automobile industry.
A. A. Ford
B. B. General Motors
C. C. Chrysler
D. D. American Motors
【单选题】
The following statements are all true except .
A. A. Agribusinesses reflect the big, corporate nature of many farm enterprises.
B. B. Agribusinesses maintain a balanced trade pattern between agricultural imports and exports.
C. C. Agribusinesses range from one-family corporations to multinational firms.
D. D. Agribusinesses include a variety of farm businesses and structures.
【单选题】
About of American crops are for export.
A. A. half
B. B. one third
C. C. one fourth
D. D. one fifth
【单选题】
President Johnson tried to build a “Great Society” by introducing various programs like the following except .
A. A. Medicare
B. B. Food Stamps
C. C. Education Initiatives
D. D. Unemployment Pension
【单选题】
The following inventions took place during the “second indThe following inventions took place during the “second industrial revolution” except .
A. A. typewriter
B. B. telephone
C. C. electric light
D. D. refrigerator
【单选题】
The first National Bank of the United States was established with the urge of .
A. A. George Washington
B. B. Thomas Jefferson
C. C. Andrew Jackson
D. D. Alexander Hamilton
【单选题】
Chartered companies were NOT granted the by the British King or Queen.
A. A. political authority
B. B. economic rights
C. C. judicial authority
D. D. diplomatic authority
【单选题】
The modern American economy progressed from to , and eventually, to .
A. A. colonial economy, handcraft economy, industrial economy
B. B. farming economy, handcraft economy, industrial economy
C. C. colonial economy, farming economy, industrial economy
D. D. handcraft economy, farming economy, industrial economy
【单选题】
America produces a major portion of the world’s products in the following fields except .
A. A. machinery
B. B. automobiles
C. C. ore
D. D. chemicals
【单选题】
The President is directly voted into office by .
A. A. all citizens of America
B. B. the citizens over 18 years old
C. C. electors elected by the voters
D. D. the senators and representatives
【单选题】
The Supreme Court is composed of justices.
A. A. six
B. B. seven
C. C. eight
D. D. nine
【单选题】
The terms for a Senator and Representative are and years respectively.
A. A. two, four
B. B. two, three
C. C. two, six
D. D. six, two
【单选题】
According to the Constitution, a candidate for President must be .
A. A. at least 35 years old
B. B. at least a 14 years’ resident of the United States
C. C. born in America
D. D. all of the above
【单选题】
The following except are all powers of the President.
A. A. vetoing any bills passed by Congress
B. B. appointing federal judges when vacancies occur
C. C. making laws
D. D. issuing executive orders
【单选题】
All the following except cannot make legislative proposal.
A. A. the Senator
B. B. the Representative
C. C. the Secretary of State
D. D. the President
【单选题】
The following except are guaranteed in the Bill of Rights.
A. A. freedom of religion
B. B. the right to get into people’s house by police
C. C. freedom of speech and of press
D. D. the right to own one’s weapon if one wishes
【单选题】
The Bill of Rights .
A. A. defines the rights of Congress and the rights of the President
B. B. guarantees citizens of the United States specific individual rights and freedoms
C. C. is part of the Declaration of Independence
D. D. has no relationship with the Constitution
【单选题】
The Constitution of the United States .
A. A. gives the most power to Congress
B. B. gives the most power to the President
C. C. tries to give each branch enough power to balance the others
D. D. gives the most power to the Supreme Court