【单选题】
当管内的液体处于紊流状态时,管截面上流速最大的地方___。
A. 在靠近管壁处;
B. 在截面中心处;
C. 在管壁和截面中心之间;
D. 根据截面大小而不同
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相关试题
【单选题】
___用于接通和切断管道中的介质。
A. 截止阀;
B. 调节阀;
C. 逆止阀;
D. 安全阀。
【单选题】
灰斗的充满系数应为___。
A. 0.6:
B. 0.8;
C. 1.0;
D. 0.5以下。
【单选题】
下列哪一种气体是属于易燃气体 ___。
A. 二氧化碳;
B. 二氧化硫;
C. 氧气;
D. 乙炔。
【单选题】
一个工作负责人只能同时发给___工作票。
A. 一 张;
B. 两张;
C. 三张;
D. 实际工作需要。
【单选题】
利用___和继电器配合可实现装置的自动控制。
A. 闸刀开关;
B. 接触器;
C. 熔断器;
D. 高压隔离开关。
【单选题】
当输送管线长度为___m时,宜采用压力式(仓泵)气力除灰系统。
A. 100~200;
B. 250~400;
C. 450~1000;
D. 1000以上。
【单选题】
防止灰斗下部漏入空气和水蒸气,一般在灰斗下面设有___。
A. 锁气器或水封;
B. 灰斗加热装置;
C. 引风机;
D. 吸风机。
【单选题】
泵的轴功率P与有效功率Pe的关系是___。
A. P=Pe;
B. P>Pe;
C. P<Pe;
D. 无法判断。
【单选题】
风机运行时,如因电流过大或摆动幅度大而跳闸,则___。
A. 可强行启动一次:
B. 可在就地监视下启动一次;
C. 不应再强行启动;
D. 不许启动。
【单选题】
电阻并联电路中,各支路电流与各支路电导___。
A. 成正比;
B. 成反比;
C. 相等;
D. 无关。
【单选题】
闸阀与___的用途基本相同。
A. 调节阀;
B. 逆止阀;
C. 截止阀;
D. 安全阀。
【单选题】
当整流升压变压器出口限流电阻烧断时,表盘显示:一次电压较低,一次电流接近零;二次电压___,二次电流为零。
A. 很高;
B. 很低;
C. 正常;
D. 为零。
【单选题】
运行中监视电机电流,电流指示应在___。
A. 规定值附近;
B. 红线附近;
C. 红线之上;
D. 接近零的位置。
【单选题】
在工程热力学中基本状态参数为压力、温度和___。
A. 内能;
B. 焓;
C. 比容;
D. 熵。
【单选题】
流体的静压力总是与作用面___。
A. 平行;
B. 垂直;
C. 垂直且指向作用面;
D. 倾斜。
【单选题】
黏度随温度升高变化的规律是___。
A. 液体和气体黏度均增大;
B. 液体黏度增大,气体黏度减小;
C. 液体黏度减小,气体黏度增大;
D. 液体和气体黏度均减小。
【单选题】
减压阀是用来___介质压力的。
A. 增加;
B. 降低;
C. 调节;
D. 都不是。
【单选题】
管路运行中起关断作用的阀门应处于___状态。
A. 全开;
B. 半关;
C. 全关或全开;
D. 90%开度。
【单选题】
放电电极附近的气体电离产生大量的___。
A. 正离子和电子;
B. 正离子和负离子;
C. 正电荷和负电荷;
D. 中子和电子。
【单选题】
二次电流和二次电压是指___。
A. 输入到整流变压器初级的直流电流和电压;
B. 输入到整流变压器初级的交流电流和电压;
C. 整流变压器输出的直流电流和电压;
D. 整流变压器输出的交流电流和电压。
【单选题】
各电场运行中,火花率最大的是第___电场。
【单选题】
一次电流和一次电压是指___ 。
A. 输入到整流变压器初级的直流电流和电压;
B. 输入到整流变压器初级的交流电流和电压;
C. 整流变压器输出的直流电流和电压;
D. 整流变压器输出的交流电流和电压。
【单选题】
在220V电源上串联下列4个灯泡,其中最亮的是___。
A. 220V、40W;
B. 220V、100W;
C. 220V、60W;
D. 250V、40W。
【单选题】
在并联电路中总电流等于各支路电流之___ 。
【单选题】
输出功率自动调节控制运行方式适用于___的场合。
A. 高比电阻粉尘和存在着易燃易爆气体;
B. 粉尘浓度高、容易产生电晕封闭;
C. 工况变化起伏比较大;
D. 运行工况好、排尘浓度较低。
【单选题】
若气力除灰系统设备可靠性较高且为单元制,则___, 但除灰系统的出力不应小于系统输送量的200%。
A. 宜设整套备用系统;
B. 必须设整套备用系统;
C. 不宜设整套备用系统;
D. 都不对。
【单选题】
利用___叫做固体膨胀式温度计。
A. 固体膨胀的性质制成的仪表;
B. 物体受热膨胀的性质制成的仪表;
C. 固体受热膨胀的性质而制成的测量仪表;
D. 物体受热膨胀制成的仪表。
【单选题】
灰渣泵中磨损最严重的部件是___。
A. 轴;
B. 轴承;
C. 叶轮和护套;
D. 轴和轴承。
【单选题】
为了防止灰渣泵停运时水向灰渣泵房倒流,在泵的出口装有___。
A. 止回阀;
B. 闸阀;
C. 放水阀;
D. 真空阀。
【单选题】
正弦交流电完成一次循环所用的时间叫___ 。
A. 周期;
B. 频率;
C. 相位;
D. 角频率。
【单选题】
一切磁现象都起源于___。
A. 电压;
B. 电阻;
C. 电流;
D. 电源。
【单选题】
电阻电路中电阻并联时起___作用。
A. 分流和分压;
B. 分压;
C. 分流;
D. 增大电阻。
【单选题】
与同扬程清水泵相比灰渣泵的叶轮___。
A. 转速高,直径大;
B. 转速高,直径小;
C. 转速低,直径大;
D. 转速低,直径小。
【单选题】
灰渣泵运行周期短的主要原因是___。
A. 流量大;
B. 扬程高;
C. 效率低;
D. 磨损严重。
【单选题】
仪表的精度等级是用___表示的。
A. 系统误差;
B. 绝对误差;
C. 允许误差;
D. 相对误差。
【单选题】
单位正电荷由高电位移向低电位时,电场力对它所做的功称为___。
A. 电压;
B. 电位;
C. 电功率;
D. 电量。
【单选题】
交接班应正点进行,交接班以___为准。
A. 双方在运行日志上签字;
B. 双方口头交待;
C. 时间;D、交班人员签字。
【单选题】
单块阳极板的悬挂方式有___。
A. 单点偏心悬挂;
B. 两点紧固连接;
C. 单点偏心悬挂和两点紧固连接;
D. 焊接和两点紧固连接。
【单选题】
间隙供电控制方式适用于___的场合。
A. 高比电阻粉尘;
B. 粉尘浓度高、容易产生电晕封闭;
C. 工况变化起伏比较大;
D. 低比电阻粉尘。
【单选题】
水在水泵中压缩升压可以看作是___。
A. 等温过程;
B. 绝热过程;
C. 等压过程;
D. 等容过程。
推荐试题
【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
【单选题】
The U. S. Constitution came into effect in .
A. A. 1787
B. B. 1789
C. C. 1791
D. D. 1793
【单选题】
The Vietnam War was a long-time suffering for Americans, and it continued throughout the terms of Presidents .
A. A. Johnson, Nixon and Ford
B. B. Truman, Eisenhower and Kennedy
C. C. Kennedy, Johnson and Nixon
D. D. Eisenhower, Kennedy and Johnson
【单选题】
President applied New Deal to deal with the problems of the Great Depression.
A. A. Wilson
B. B. Truman
C. C. Roosevelt
D. D. Kennedy
【单选题】
The policy of the United States was at the beginning of the two world wars.
A. A. neutrality
B. B. full involvement
C. C. partial involvement
D. D. appeasement
【单选题】
Abraham Lincoln issued to grant freedom to all slaves.
A. A. Declaration of Independence
B. B. Constitution
C. C. Emancipation Proclamation
D. D. Bill of Rights
【单选题】
In May 1775, was held in Philadelphia and began to assume the functions of a national government.
A. A. the First Continental Congress
B. B. the Second Continental Congress
C. C. the Boston Tea Party
D. D. the Congress of Confederation
【单选题】
The first shots of the American dependence were fired in .
A. A. Concord
B. B. Lexington
C. C. Philadelphia
D. D. Boston
【单选题】
“No taxation without representation” was the rallying slogan of .
A. A. the settlers of Virginia
B. B. the people of Pennsylvania
C. C. the colonists in New England
D. D. the people of the 13 colonies
【单选题】
The Seven Years’ War occurred between the .
A. A. French and American Indians
B. B. French and Spaniards
C. C. French and British
D. D. British and American Indians
【单选题】
Pilgrim Fathers are a group of who came to America to avoid persecution in England.
A. A. Protestants
B. B. Puritans
C. C. Catholics
D. D. Christians
【单选题】
The first successful English colony in North America was founded at in .
A. A. Jamestown, Louisiana
B. B. Boston, Massachusetts
C. C. Jamestown, Virginia
D. D. Plymouth, Georgia
【单选题】
The characteristic of dominant American culture is .
A. A. English-speaking, northern European, Roman Catholic and middle-class
B. B. English-speaking, western European, Roman Catholic and upper-class
C. C. English-speaking, northern European, Protestant and upper-class
D. D. English-speaking, western European, Protestant and middle-class
【单选题】
The ImmiWar of Ingrants Act of 1924 restricted the further immigration into the United States, particularly from .
A. A. Europe
B. B. Asia
C. C. Africa
D. D. South America
【单选题】
The largest minority in the United States is the .
A. A. Pacific Islanders
B. B. Blacks
C. C. Native Americans
D. D. Asians
【单选题】
The native Alaskan population includes the following except the .
A. A. Indians
B. B. Eskimos
C. C. Aleuts
D. D. Blacks
【单选题】
is located on the U. S. –Canadian border between Lake Erie and Lake Ontario.
A. A. Yellowstone National Park
B. B. The Grand Canyon
C. C. Niagara Falls
D. D. The Great Salt Lake
【单选题】
Some of the world famous universities like Harvard, Yale and MIT are located .
A. A. in the South
B. B. along the Pacific Coast
C. C. in New England
D. D. in the Midwest