【单选题】
感应电流的方向总是使感应电流的磁场阻碍引起感应电流的磁通的变化,这一定律称为( )。 ___
A. 法拉第定律
B. 特斯拉定律
C. 楞次定律
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相关试题
【单选题】
旋转磁场的旋转方向决定于通入定子绕组中的三相交流电源的相序,只要任意调换电动机( )所接交流电源的相序,旋转磁场既反转。 ___
【单选题】
螺旋式熔断器的电源进线应接在( )。 ___
【单选题】
引起电光性眼炎的主要原因是( )。 ___
【单选题】
按照计数方法,电工仪表主要分为指针式仪表和( )式仪表。 ___
【单选题】
使用剥线钳时应选用比导线直径( )的刃口。 ___
【单选题】
更换熔体时,原则上新熔体与旧熔体的规格要( )。 ___
【单选题】
铁壳开关在作控制电机启动和停止时,要求额定电流要大于或等于( )倍电动机额定电流。 ___
【单选题】
胶壳刀开关在接线时,电源线接在( )。 ___
A. 下端(动触点)
B. 上端(静触点)
C. 两端都可
【单选题】
低压电工作业是指对( )V以下的电气设备进行安装、调试、运行操作等的作业。 ___
【单选题】
绝缘安全用具分为( )安全用具和辅助安全用具。 ___
【单选题】
下列现象中,可判定是接触不良的是( )。 ___
A. 灯泡忽明忽暗
B. 日光灯启动困难
C. 灯泡不亮
【单选题】
熔断器的额定电流( )电动机的起动电流。 ___
【单选题】
降压启动是指启动时降低加在电动机( )绕组上的电压,启动运转后,再使其电压恢复到额定电压正常运行。 ___
【单选题】
特种作业操作证有效期为( )年。 ___
【单选题】
电流继电器使用时其吸引线圈直接或通过电流互感器（ ）在被控电路中。 ___
【单选题】
下列灯具中功率因数最高的是（ ）。___
【单选题】
一般照明场所的线路允许电压损失为额定电压的（ ）。 ___
【单选题】
静电防护的措施比较多，下面常用又行之有效的可消除设备外壳静电的方法是（ ）。 ___
【单选题】
三个阻值相等的电阻串联时的总电阻是并联时总电阻的（ ）倍。 ___
【单选题】
稳压二极管的正常工作状态是（ ）。 ___
A. 截至状态
B. 导通状态
C. 反向击穿状态
【单选题】
（ ）的电机，在通电前，必须先做各绕组的绝缘电阻检查，合格后才可通电。 ___
A. 一直在用，停止没超过一天
B. 不常用，但电机刚停止不超过一天
C. 新装或未用过的
【单选题】
将一根导线均匀拉长为原长的 2 倍，则它的阻值为原阻值的（ ）倍。 ___
【单选题】
笼形异步电动机降压启动能减少启动电流，但由于电机的转矩与电压的平方成（ ）因此降压启动时转矩减少较多。 ___
【单选题】
低压配电柜灭火可选用的灭火器是（ ）。 ___
A. 二氧化碳灭火器
B. 泡沫灭火器
C. 水基式灭火器
【单选题】
漏电保护断路器在设备正常工作时，电路电流的相量和（ ），开关保持闭合状态。 ___
【单选题】
导线接头电阻要足够小，与同长度同截面导线的电阻比不大于（ ）。 ___
【单选题】
对照电机与其铭牌检查，主要有（ ）、频率、定子绕组的连接方法。 ___
【单选题】
电机在正常运行时的声音，是平稳、轻快、（ ）和有节奏的。 ___
【单选题】
笼形异步电动机常用的降压启动有（ ）启动、自耦变压器降压启动、星-三角降压启动。 ___
A. 串电阻降压
B. 转子串电阻
C. 转子串频敏
【单选题】
具有反时限安秒特性的元件就具备短路保护和（ ）保护能力。___
【单选题】
落地插座应具有牢固可靠的（ ）。 ___
【单选题】
纯电容元件在电路中（ ）电能。 ___
【单选题】
载流导体在磁场中将会受到（ ）的作用。 ___
【单选题】
一般线路中的熔断器有（ ）保护。 ___
【单选题】
某四极电动机的转速为 1440r/min，则这台电动机的转差率为（ ）%。 ___
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【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
My parents do not object to my taking part-time jobs, but they remind me not to let them [ ] my school work
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
Anger, worry, disappointment, these negative emotions [ ] your heart, brain and body
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
If a person adopts an unhealthy lifestyle, he will surely be [ ]developing diseases.
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
Most people were ready to give up on him when he [ ] of school, but later he returned and earned his degree
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
Drinking too much can increase the risk of developing high blood pressure, which [ ] can lead to heart attack or stroke
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
Low-cost airlines are emerging all over Asia; this will [ ]the development of the worlds air-travel market as a whole
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
When you move to a new country, you may find the food there strange and you may miss the familiar smells of the food [ ] in your country
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
Although he kept trying and failing, I always [ ] the belief that he would succeed one day.
【填空题】
take a toll on，in other words ，drop out，in turn ，at risk (of) ，interfere with，be accustomed to， contribute to，cut back on ，hold on to
The tax only affects people with an annual income over $200,000-[ ], it will only attect the very rich.
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Studies[ ]that children who often take part in cooperative programs benefit a lot more than other children
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
They are such a(n) [ ] family- they must have been shocked when their son dyed(染) his hair pink,
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Testing students by examinations has long been regarded as a reliable way to [ ]students'ability
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Many power stations have been modernized to give off less pollution, or they were moved further away from the living areas in order to [ ] the damage,
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Unemployment has come down slightly, but this does not [ ]the fact that it is still a major problem
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Mr. Smith is not doing well; the doctor told us that several colds [ ]his health
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
The best way to deal with problems at home is to talk things out calmly and honestly and try to reach a(n) [ ]
【填空题】
open the door to，In advance，all at once，reap the benefits (of)， make the most of，over time， get by， stand a chance (of)，remind of， take pleasure in，
Experts say our company is amazing in that sales have been increasing steadily [ ]
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
After 10 years of full-time training, she has,finally [ ] as a professional dancer.
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
[ ], what is the point in taking part in the competitive event if the result is only to prove how incompetent you are?,
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
Redecorating the house is a challenging task. It's necessary to [ ] the wallpaper first.
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
I never really had any problems with change. On the contrary, I welcome change [ ]
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
A lot of what we [ ] is made from raw materials which are not renewable
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
Megan and John realized that their house was too messy for a new baby, so they decided to [ ] their house before the baby was born
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
Jennifer couldn't [ ] her tears when she saw the sick children at a new blood cancer center in Virginia
【填空题】
make it， with open arms ，strip off，keep back，
free of/ from ，after all，straighten up， throw away
We want to give all children a world [ ] violence
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
Fortunately, the accident didn't [ ] many people, for there was little traffic at that hour.
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
She[ ] her ambition of becoming a fashion designer after years of hard work
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
They kept on trying their best to develop
their business, but in such [ ]market competition, they had no Idea if success would come along one day
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
As music plays an important role in our life, many music teachers and educators [ ] taking up a musical instrument at a young age
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
This rule should be entirely clear in the minds of everyone and should not be misunderstood under any [ ]
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
My daughter was shy; she was afraid to ask questions,[ ] to questions in class,or talk with other children
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
I got from him only a letter, which was put on my office desk; [ ] to the receipt of this letter I have never heard from him
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
The duties to provide services for children in need are not [ ] to the local social services department
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
We pray that all nations be [ ] and that all people around the world live in peace
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
It was reported the president had [ ]to fight If war was necessary,even if it meant destroying his chances of re-election
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
I had to [ ] one of my email accounts as it was filled with junk mail
【填空题】
controversial，assess， resolve，decrease，alter，abandon，indicate，undermine，compromise， conventional
Darwin's theory of evolution remains[ ] partly because it challenges the religious belief that God created man
【填空题】
advocate，involve，confine，respond，subsequent ，distinct ，intense， fulfill，circumstance， reconcile
He suggested a small but [ ] improvement on our former plan; I really appreciate it.
【填空题】
in sb. 's words，count on，make sense of ，reserve for， shield from，call on， sum up， relate to ，in need，
be/ get caught up in
She held her hand above her eyes to [ ]them [ ] the sun so that she could see more clearly the man in front of her
【填空题】
in sb. 's words，count on，make sense of ，reserve for， shield from，call on， sum up， relate to ，in need，
be/ get caught up in
The boy studied the signs for over an hour,but still could not [ ]them, so he turned to his teacher for help
