相关试题
【单选题】
单结晶体管在电路图中的文字符号是___。
【单选题】
集成运放的输出级通常由___构成。
A. 互补对称射极放大电路
B. 共射放大电路
C. 共基极放大电路
D. 共集电极放大电路
【单选题】
理想集成运放输出电阻为___
A. 10Ω
B. 100Ω
C. OΩ
D. 1KΩ
【单选题】
固定偏置共射极放大电路，已知RB=300KΩ，RC=4KΩ，Vcc=12V，β=50，则UCEQ为___V 。
【单选题】
分压式偏置共射放大电路，更换β大的管子，其静态值UCEQ会___
A. 无法确定
B. 变小
C. 不变
D. 增大
【单选题】
固定偏置共射放大电路出现饱和失真，是___
A. Rc偏小
B. RB偏大
C. Rc偏大
D. RB偏小
【单选题】
多级放大电路之间，常用共集电极放大电路，是利用其___特性。
A. 输入电阻大、输出电阻小
B. 输入电阻小、输出电阻大
C. 输入电阻小、输出电阻小
D. 输入电阻大、输出电阻大
【单选题】
共射极放大电路的输出电阻比共基极放大电路的输出电阻是___。
【单选题】
能用于传递交流信号且具有阻抗匹配的耦合方式是___。
A. 阻容耦合
B. 变压器耦合
C. 电感耦合
D. 直接耦合
【单选题】
要稳定输出电流，增大电路输入电阻应选用___负反馈。
A. 电压并联
B. 电压串联
C. 电流串联
D. 电流并联
【单选题】
音频集成功率放大器的电源电压一般为___伏。
【单选题】
RC选频振荡电路，当电路发生谐振时，选频电路的幅值为___。
【单选题】
LC选频振荡电路达到谐振时，选频电路的相位移为___度。
【单选题】
串联型稳压电路的调整管接成___电路形式。
A. 共射极
B. 分压式共射极
C. 共基极
D. 共集电极
【单选题】
单相半波可控整流电路电感性负载接续流二极管，α=90°时，输出电压Ud为___
A. 0.45 U2
B. 0.9 U2
C. 0.225 U2
D. 1.35 U2
【单选题】
单相桥式可控整流电路电感性负载带续流二极管时，晶闸管的导通角为___
A. 90°-α
B. 180°-α
C. 90°+α
D. 180°+α
【单选题】
单相桥式可控整流电路电感性负载，控制角α=60°时，输出电压Ud是___
A. 1.17U2
B. 0.9U2
C. 0.45U2
D. 1.35U2
【单选题】
___触发电路输出尖脉冲。
A. 交流变频
B. 脉冲变压器
C. 集成
D. 单结晶体管
【单选题】
晶闸管两端___的目的是实现过压保护。
A. 串联快速熔断器
B. 并联快速熔断器
C. 并联压敏电阻
D. 串联压敏电阻
【单选题】
熔断器的额定分断能力必须大于电路中可能出现的最大___
A. 过载电流
B. 启动电流
C. 工作电流
D. 短路电流
【单选题】
控制和保护含半导体器件的直流电路中宜选用___断路器
A. 塑壳式
B. 限流型
C. 框架式
D. 直流快速断路器
【单选题】
接触器的额定电流应不小于被控电路的___
A. 额定电流
B. 负载电流
C. 峰值电流
D. 最大电流
【单选题】
中间继电器的选用依据是控制电路的电压等级、___、所需触点的数量和容量等。
A. 短路电流
B. 电流类型
C. 阻抗大小
D. 绝缘等级
【单选题】
选用LED指示灯的优点之一是___
A. 寿命长
B. 发光强
C. 价格低
D. 颜色多
【单选题】
JBK系列控制变压器适用于机械设备一般电器的控制、工作照明、___的电源之用。
A. 油泵
B. 电动机
C. 信号灯
D. 压缩机
【单选题】
压力继电器选用时首先要考虑所测对象的压力范围，还要符合电路中的额定电压，___，所测管路接口管径的大小。
A. 触点的功率因数
B. 触点的电阻率
C. 触点的绝缘等级
D. 触点的电流容量
【单选题】
直流电动机结构复杂、价格贵、制造麻烦、维护困难，但是启动性能好、___。
A. 调速范围大
B. 调速力矩大
C. 调速力矩小
D. 调速范围小
【单选题】
直流电动机的定子由机座、主磁极、换向极、___、端盖等组成。
A. 换向器
B. 电枢
C. 转轴
D. 电刷装置
【单选题】
并励直流电动机的励磁绕组与___并联。
A. 电枢绕组
B. 稳定绕组
C. 补偿绕组
D. 换向绕组
【单选题】
直流电动机降低电枢电压调速时，转速只能从额定转速___。
A. 往下降
B. 开始反转
C. 往上升
D. 升高一倍
【单选题】
直流电动机的各种制动方法中，最节能的方法是___。
A. 回馈制动
B. 机械制动
C. 反接制动
D. 能耗制动
【单选题】
直流他励电动机需要反转时，一般将___两头反接。
A. 补偿绕组
B. 电枢绕组
C. 励磁绕组
D. 换向绕组
【单选题】
直流电动机滚动轴承发热的主要原因有___等。
A. 电刷架位置不对
B. 电动机受潮
C. 轴承变形
D. 轴承磨损过大
【单选题】
设计多台电动机顺序控制线路的目的是保证操作过程的合理性和___
A. 节约电能的要求
B. 工作的安全可靠
C. 降低噪声的要求
D. 减小振动的要求
【单选题】
三相异步电动机的位置控制电路中，除了用行程开关外，还可用___
A. 光电传感器
B. 速度继电器
C. 断路器
D. 热继电器
【单选题】
下列不属于位置控制线路的是___
A. 龙门刨床的自动往返控制电路
B. 工厂车间里行车的终点保护电路
C. 走廊照明灯的两处控制电路
D. 电梯的开关门电路
【单选题】
三相异步电动机采用___时，能量消耗小，制动平稳。
A. 发电制动
B. 回馈制动
C. 能耗制动
D. 反接制动
【单选题】
三相异步电动机能耗制动的控制线路至少需要___个按钮。
推荐试题
【单选题】
In 1914, an apparently insignificant event in a remote part of Eastern Europe __________ Europe into a great war.
A. inserted
B. imposed
C. pitched
D. plunged
【单选题】
We had to ___________ a lot of noise when the children were at home.
A. go in for
B. hold on to
C. put up with
D. keep pace with
【单选题】
A person's calorie requirements vary ______ his life.___
A. across
B. throughout
C. over
D. within
【单选题】
Generous public funding of basic science would ________considerable benefits for the country's health, wealth and security.___
A. lead to
B. result from
C. lie in
D. settle down
【单选题】
In a time of social reform, people's state of mind tends to keep ___________ with the rapid changes of society___
A. step
B. progress
C. pace
D. touch
【单选题】
The speech which he made __________ the project has bothered me greatly.___
A. regarded
B. concerned
C. regarding
D. concerning
【单选题】
Harry was _______ by a bee when he was collecting the honey.___
A. stung
B. stuck
C. bitten
D. scratched
【单选题】
The thief tried to open the locked door but _________.___
A. in no way
B. in vain
C. without effect
D. at a loss
【单选题】
Remember that customers don't ________ about prices in that city.___
A. debate
B. consult
C. dispute
D. bargain
【单选题】
I hope that you'll be more careful in typing the letter. Don't _________ anything.___
A. lack
B. withdraw
C. omit
D. leak
【单选题】
The tomato juice left brown __________ on the front of my jacket.___
A. spot
B. point
C. track
D. trace
【单选题】
The committee is totally opposed ________ any changes being made in the plans.___
A. of
B. on
C. to
D. against
【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
