相关试题
【单选题】
将三相对称负载在同一电源上作星形连接时，负载取用的功率是作三角形连接时的___。
A. 3倍
B. √3倍
C. 1/ √3倍
D. 1/3
【单选题】
当电源电压和负载的有功功率一定时，功率因数越低，电源提供的电流就___。
A. 越大
B. 越小
C. 恒定不变
D. 不确定
【单选题】
提高功率因数的目的之一是___。
A. 节约用电，增加电动机输出功率
B. 减小无功功率，提高电源利用率
C. 降低电气设备损坏率
D. 提高电动机效率
【单选题】
提高功率因数，不正确的方法是___。
A. 在感性负载两端并联电容器
B. 视负载大小合理选用电动机
C. 电路中增加电阻性负载
D. 尽量不让电动机空转
【单选题】
电气控制线路图中，各组成电路的功能和作用在___的方格中标明。
A. 图下部
B. 图左侧
C. 图右侧
D. 图上部
【单选题】
电气控制线路，一般是由___执行对电动机的控制。
A. 按钮
B. 接触器
C. 熔断器
D. 热继电器
【单选题】
使用500型万用表测量一个800～900 的电阻，“ ”挡的量限倍率应选用___。
A. R×1
B. R×10
C. R×100
D. R×1 k
【单选题】
客车24 V/48 V电力配线绝缘电阻测量，应使用___级兆欧表。
A. 250 V
B. 500 V
C. 1 000 V
D. 2 500 V
【单选题】
绝缘材料的耐热等级为A级，最高允许工作温度为___。
A. 105 ℃
B. 120 ℃
C. 130 ℃
D. 155 ℃
【单选题】
绝缘材料的耐热等级为B级，最高允许工作温度为___。
A. 105 ℃
B. 120 ℃
C. 130 ℃
D. 155 ℃
【单选题】
客车新制灯具的绝缘电阻值，在环境温度为20 ℃，相对湿度为60％的情况下，应不低于___。
A. 2 M
B. 5 M
C. 8 M
D. 10 M
【单选题】
我国客车空调制冷装置采用的制冷剂主要是___。
【单选题】
KZS/M-Ⅰ型轴报器中液晶显示器的D0～D7为___。
A. LCD的数据线
B. 读写线
C. LCD模块寄存器选择线
D. 液晶显示用电源
【单选题】
列车空调制冷剂氟利昂22(R22)的蒸发温度是___。
A. －40.8 ℃
B. －29.8 ℃
C. －31 ℃
D. －25 ℃
【单选题】
客车空调机组的电预热器所设置的温度开关式电热保护器断开值是___。
A. 70 ℃±5 ℃
B. 80 ℃±5 ℃
C. 90 ℃±5 ℃
D. 100 ℃±5 ℃
【单选题】
轴温监测与报警装置的抗干扰电源，通常采用___将直流电逆变为交流电，再由交流电整流成直流电。
A. 晶体管逆变器
B. 变压器
C. 可控硅
D. 不能确定
【单选题】
热继电器整定电流为电动机额定电流的1.50倍时，热继电器动作时间小于等于___。
A. 1 min
B. 2 min
C. 3 min
D. 4 min
【单选题】
客车荧光灯逆变器是以___作为基本元件的。
A. 二极管
B. 三极管
C. 晶闸管
D. 单结晶体管
【单选题】
KZS/M-Ⅰ型轴报器中液晶显示器的R/W为___。
A. LCD的数据线
B. 读写线
C. LCD模块寄存器选择线
D. 液晶显示用电源
【单选题】
982型应急电源箱整流器额定输出电流为___。
A. 50 A
B. 35 A
C. 10 A
D. 15 A
【单选题】
982型应急电源箱充电机充电电流为___。
A. 20 A
B. 5 A
C. 10 A
D. 2 A
【单选题】
981型应急电源箱整流器额定输出电流为___。
A. 50 A
B. 35 A
C. 5 A
D. 15 A
【单选题】
981型应急电源箱充电机充电电流为___。
A. 20 A
B. 5 A
C. 10 A
D. 2 A
【单选题】
运用列车漏电电流在相对湿度大于80％时，不得大于___。
A. 30 mA
B. 60 mA
C. 80 mA
D. 10 mA
【单选题】
铅蓄电池放电过量，如电压在1.75 V以下，密度在1.20 g/cm3以下继续放电，则会造成蓄电池___。
A. 极板腐蚀
B. 极板硫化
C. 极板短路
D. 极板脱落
【单选题】
由磁路欧姆定律可知，电磁设备要获得一定的磁通，磁路中气隙越大，所需励磁电流___。
A. 越大
B. 越小
C. 不变
D. 无法确定
【单选题】
装有空气调节装置的旅客列车，在冬季工况时，全列车负载的功率因数应接近于___。
A. 0.5
B. 0.6
C. 0.8
D. 1
【单选题】
KZS/M-Ⅰ型轴报器中液晶显示器的RS为___。
A. LCD的数据线
B. 读写线
C. LCD模块寄存器选择线
D. 液晶显示用电源
【单选题】
J5型感应子发电机额定频率为___。
A. 50 Hz
B. 100 Hz
C. 85～370 Hz
D. 114～495 Hz
【单选题】
三相同步电动机在启动时，其转子绕组必须___。
A. 开路
B. 短路
C. 加入直流励磁
D. 通过电阻短接
【单选题】
采用集中供电的硬卧车，白炽灯照明的平均照度应不低于___。
A. 80 lx
B. 100 lx
C. 120 lx
D. 150 lx
【单选题】
测量空调客车100 V以下线路及用电设备的绝缘电阻，应使用___级兆欧表。
A. 500 V
B. 1 000 V
C. 100 V
D. )2 500 V
【单选题】
运用空调客车电力绝缘值在相对湿度小于60％时，单辆不得低于___。
A. 0.5 M
B. 1 M
C. 2 M
D. 0.2 M
【单选题】
KLC40型空调机组在半冷工况下，通风机应___运转。
A. 低速
B. 高速
C. 低速或高速
D. 不确定
【单选题】
KLC40型空调机组在全冷工况下，通风机应___运转。
A. 低速或高速
B. 低速
C. 高速
D. 不确定
【单选题】
我国规定___以下的电压为安全电压。
A. 36 V
B. 48 V
C. 110 V
D. 220 V
【单选题】
检修发电车柴油机启动蓄电池时，其容量小于___时，应予以更换。
A. 70％
B. 75％
C. 80％
D. 85％
【单选题】
餐车冰箱电动机启动后工作电流应小于或等于___。
A. 25 A
B. 30 A
C. 35 A
D. 40 A
【单选题】
R12的正常蒸发温度为___。
A. －40.8 ℃
B. －29.8 ℃
C. 40.8 ℃
D. 29.8 ℃
【单选题】
电子防滑装置是由电子防滑单元、___、测速齿轮、防滑阀、端子盒、压力开关等部分组成。
A. 速度传感器
B. 温度传感器
C. 低压传感器
D. 高压传感器
推荐试题
【单选题】
I'm very sorry to have _______ you with so many questions on such an occasion.___
A. interfered
B. offended
C. impressed
D. bothered
【单选题】
The price of beer _______ from 50 cents to $4 per liter during the summer season.___
A. altered
B. ranged
C. separated
D. differed
【单选题】
Their son doesn't know what to ________ at the university; he can't make up his mind about his future.___
A. take in
B. take up
C. take over
D. take after
【单选题】
Although they plant trees in this area every year, the tops of some hills are still _________.___
A. blank
B. hollow
C. vacant
D. bare
【单选题】
Being a pop star can be quite a hard life, with a lot of traveling ________ heavy schedules.
A. with regard to
B. as to
C. in relation to
D. owing to
【单选题】
Tony is very disappointed _______ the results of the exam.
A. with
B. for
C. toward
D. on
【单选题】
William Penn, the founder of Pennsylvania, _________ defended the right of every citizen to freedom of choice in religion.
A. peculiarly
B. indifferently
C. vigorously
D. inevitably
【单选题】
When people become unemployed, it is _______ which is often worse than lack of wages.___
A. laziness
B. poverty
C. idleness
D. inability
【单选题】
In previous times, then fresh meat was in short __________, pigeons were kept by many households as a source of food.
A. store
B. provision
C. reserve
D. supply
【单选题】
Those gifts of rare books that were given to us were deeply _________.___
A. appreciated
B. approved
C. appealed
D. applied
【单选题】
It is our ___________ policy that we will achieve unity through peaceful means.___
A. consistent
B. continuous
C. considerate
D. continual
【单选题】
He is __________ about his chances of winning a gold medal in the Olympics next year.___
A. optimistic
B. optional
C. outstanding
D. obvious
【单选题】
The director was critical _______________ the way we were doing the work.___
A. at
B. in
C. of
D. with
【单选题】
In a sudden _____________ of anger, the man tore up everything within reach.___
A. attack
B. burst
C. split
D. blast
【单选题】
In Britain people _____________ four million tons of potatoes every year.___
A. swallow
B. dispose
C. consume
D. exhaust
【单选题】
I'd _____________ his reputation with other farmers and business people in the community, and then make a decision about whether or not to approve a loan.___
A. take into account
B. account for
C. make up for
D. make out
【单选题】
She cooked the meat for a long time so as to make it _____________ enough to eat.___
A. mild
B. slight
C. light
D. tender
【单选题】
The computer revolution may well change society as _____________ as did the Industrial Revolution.___
A. certainly
B. insignificantly
C. fundamentally
D. comparatively
【单选题】
A lot of ants are always invading my kitchen. They are a thorough ___________.___
A. nuisance
B. trouble
C. worry
D. anxiety
【单选题】
As we can no longer wait for the delivery of our order, we have to _________ it.___
A. postpone
B. refuse
C. delay
D. cancel
【单选题】
When a fire _________ at the National Exhibition in London, at least ten priceless paintings were completely destroyed.___
A. broke of
B. broke out
C. broke down
D. broke up
【单选题】
The destruction of these treasures was a loss for mankind that no amount of money could __________.___
A. stand up to
B. make up for
C. come up with
D. put up with
【单选题】
The student was just about to ___________ the questions, when suddenly he found the answer.___
A. arrive at
B. submit to
C. work out
D. give up
【单选题】
When there are small children around, it is necessary to put bottles of pills out of _________.___
A. reach
B. hand
C. hold
D. place
【单选题】
The _________ of blood always makes him feel sick.___
A. sight
B. view
C. look
D. form
【单选题】
In Britain, the best season of the year is probably __________ spring.___
A. later
B. last
C. latter
D. late
【单选题】
Free medical treatment in this country covers sickness of mind as well as _________ sickness.___
A. normal
B. regular
C. average
D. ordinary
【单选题】
Although he had looked through all the reference material on the subject, he still found it hard to understand this point and her explanation only _________ to his confusion.___
A. extended
B. amounted
C. added
D. turned
【单选题】
A completely new situation will ___________ when the examination system comes into existence.___
A. arise
B. rise
C. raise
D. arouse
【单选题】
Cancer is second only __________ heart disease as a cause of death.___
A. of
B. to
C. with
D. from
【单选题】
The manager needs an assistant that he can _________ to take care of problems in his absence.___
A. count on
B. count in
C. count up
D. count out
【单选题】
We gave out a cheer when the red roof of the cottage came __________ view.___
A. from
B. in
C. before
D. into
【单选题】
They took ________ measures to prevent poisonous gases from escaping.___
A. fruitful
B. beneficial
C. valid
D. effective
【单选题】
Doing your homework is a sure way to improve your test scores, and this is especially true _______ it comes to classroom tests.___
A. when
B. since
C. before
D. after
【单选题】
In developing countries people are _______ into overcrowded cities in great numbers.___
A. breaking
B. filling
C. pouring
D. hurrying
【单选题】
There are other problems which I don't propose to ____________ at the moment.___
A. go into
B. go around
C. go for
D. go up
【单选题】
It is quite necessary for a qualified teacher to have good manners and _________ knowledge.___
A. extensive
B. expansive
C. intensive
D. expensive
【单选题】
I'm not sure whether I can gain any profit from the investment, so I can't make a(n) ______ promise to help you.___
A. exact
B. defined
C. definite
D. sure
【单选题】
The sports meet, originally due to be held last Friday, was finally ________ because of the bad weather.___
A. set off
B. broken off
C. worn off
D. called off
【单选题】
It has been revealed that some government leaders _______ their authority and position to get illegal profits for themselves.___
A. employ
B. take
C. abuse
D. overlook
