【判断题】
刀开关在作隔离开关选用时，要求刀开关的额定电流要大于或等于线路实际的故障电流。
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相关试题
【判断题】
组合开关可直接起动5KW以下的电动机。
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电动势的正方向规定为从低电位指向高电位，所以测量时电压表应正极接电源负极、而电压表负极接电源的正极。
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接地电阻测试仪就是测量线路的绝缘电阻的仪器。
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电压的大小用电压表来测量，测量时将其串联在电路中。
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万用表使用后，转换开关可置于任意位置。
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交流发电机是应用电磁感应的原理发电的。
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交流电每交变一周所需的时间叫做周期T。
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欧姆定律指出，在一个闭合电路中，当导体温度不变时，通过导体的电流与加在导体两端的电压成反比，与其电阻成正比。
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《安全生产法》所说的“负有安全生产监督管理职责的部门”就是指各级安全生产监督管理部门。
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在设备运行中，发生起火的原因是电流热量是间接原因，而火花或电弧则是直接原因。
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旋转电器设备着火时不宜用干粉灭火器灭火。
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事故照明不允许和其它照明共用同一线路。
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接了漏电开关之后，设备外壳就不需要再接地或接零了。
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低压验电器可以验出500V以下的电压。
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锡焊晶体管等弱电元件应用100W的电烙铁。
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为改善电动机的启动及运行性能，笼形异步电动机转子铁芯一般采用直槽结构。
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用星-三角降压启动时，启动转矩为直接采用三角形联结时启动转矩的1/3。
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转子串频敏变阻器启动的转矩大，适合重载启动。
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同一电器元件的各部件分散地画在原理图中，必须按顺序标注文字符号。
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对电机轴承润滑的检查，可通电转动电动机转轴，看是否转动灵活，听有无异声。
【判断题】
使用改变磁极对数来调速的电机一般都是绕线型转子电动机。
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电机在检修后，经各项检查合格后，就可对电机进行空载试验和短路试验。
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根据用电性质，电力线路可分为动力线路和配电线路。
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导线连接后接头与绝缘层的距离越小越好。
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导线接头的抗拉强度必须与原导线的抗拉强度相同。
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在电压低于额定值的一定比例后能自动断电的称为欠压保护。
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在我国，超高压送电线路基本上是架空敷设。
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一般情况下，接地电网的单相触电比不接地的电网的危险性小。
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通电时间增加，人体电阻因出汗而增加，导致通过人体的电流减小。
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触电者神志不清，有心跳，但呼吸停止，应立即进行口对口人工呼吸。
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绝缘棒在闭合或拉开高压隔离开关和跌落式熔断器，装拆携带式接地线，以及进行辅助测量和试验使用。
【判断题】
常用绝缘安全防护用具有绝缘手套、绝缘靴、绝缘隔板、绝缘垫、绝缘站台等。
推荐试题
【单选题】
Q1: Why is surfing the man’s favorite activity?___
A. Because he likes the sunny weather.
B. Because he wants to challenge himself .
C. Because it can help solve his sleeping problem .
D. Because it can help him forget all his troubles .
【单选题】
Q2: What is the woman going to do this weekend?___
A. To go sailing .
B. To go surfing .
C. To go to the beach .
D. To go to her nephew's .
【单选题】
Q3: What does the woman love doing?___
A. Going to visit relatives.
B. Enjoying the warm sun on the beach .
C. Building sand castles with her niece and nephew .
D. Playing in the sand and jumping in the waves .
【单选题】
Q4: What does the man remember doing with his brothers?___
A. Surfing in the sea .
B. Collecting seashells .
C. Building sand castles .
D. Jumping in the waves .
【单选题】
Q1: According to the survey, what percentage of British adults watched TV in theirfree time?___
A. 89 percent .
B. 84 percent .
C. 76 percent .
D. 71 percent .
【单选题】
Q2: Which age group would be the most likely to visit their friends and relatives?___
A. People aged 16 to 24
B. People aged 25 to 34 .
C. People aged 16 and over .
D. People aged 55 and over .
【单选题】
Q3: What does the speaker say about listening to music as a leisure activity for British people?___
A. People aged 16 to 24 preferred listening to music most .
B. It was getting more and more popular among the British people .
C. It was the third most popular activity among people aged 55 and over .
D. People aged 25 to 34 listened to music more often than those aged 16 to 24 .
【单选题】
Q4: According to the survey, how are leisure activities related to age?___
A. Older people go out to pubs more often . frequently .
B. Younger people go to the cinema less frequently.
C. Older people spend more time reading and gardening .
D. Younger people spend less time visiting friends and family .
【单选题】
Q1: Why was the girl excited?___
A. She is going to have a lot of vanilla ice cream .
B. She won the spelling competition at her school .
C. She is going to the state capital for a competition .
D. She "excellence"correctly,but others didn't .
【单选题】
Q2: What happened when the man was 13 years old?___
A. His family moved to Sacramento to settle down .
B. His family bought him a new suit and a new tie .
C. He went to Sacramento for a spelling competition .
D. He won the first prize in the state spelling competition .
【单选题】
Q3: Why did the man’s mom give him a big hug?___
A. To make him feel better after he lost the first prize .
B. To apologize for not buying him some ice cream .
C. To wish him good luck in the next competition .
D. To congratulate him on winning the first prize .
【单选题】
Q4: What color is the girl going to wear for her next competition?___
A. Red .
B. Blue .
C. Green .
D. Yellow .
【单选题】
Q1: What is this passage mainly about?___
A. Superstitions and science .
B. Tips on how to have good luck .
C. Superstitions in the United States .
D. Rational and superstitious societies .
【单选题】
Q2: According to the passage, what is considered as bad luck?___
A. Walking under a ladder .
B. Dreaming of a black cat .
C. Hanging a mirror in the house .
D. Stepping on one's own shadow .
【单选题】
Q3: Why is it considered bad luck to see a black cat crossing one’s path?___
A. Because black cats look like witches . e witches .
B. Because black cats were thought to be witches .
C. Because black cats bring seven years of bad luck .
D. Because black cats are hard to notice in darkness .
【单选题】
Q4: According to the passage, what will bring people good luck?___
A. Breaking a mirror on purpose .
B. Catching a falling leaf on one's birthday .
C. Finding a on the ground and picking it up .
D. Dreaming of blowing out the candles in one blow .
【单选题】
Q1: How long will the woman spend on her way to and from work by high-speed train?___
A. 4 hours .
B. 2 hours .
C. 1.5 hours .
D. 45 minutes .
【单选题】
Q2: When does the woman arrive back home by subway?___
A. At 8 .
B. At 7 .
C. At 6 .
D. At 5 .
【单选题】
Q3: According to the woman, in what way will the new high-speed train be a big help to her?___
A. She can either read or rest a little on the train .
B. She can read and respond to emails onthe train .
C. She can travel to many different parts of the city .
D. She can go shopping on her way home from work .
【单选题】
Q4: How will the new high-speed train affect the man?___
A. He can take the train to the old part of the city .
B. He can save a lot of money when he takes the train .
C. He can save 20 minutes to go to work with the train .
D. He can take the train to the airport instead of driving .
【单选题】
Q1: How much time on average do Americans spend on their way to work?___
A. About an hour .
B. More than an hour .
C. About half an hour .
D. More than one and a half hours .
【单选题】
Q2: What is the present situation about Americans’ commuting to work?___
A. More and more Americans spend over an hour getting to work .
B. Over 10 percent of Americans spend less than an hour getting to work .
C. Only New York people spend more than 90 minutes getting to work .
D. Over 10 percent of Americans spend more than 90 minutes getting to work .
【单选题】
Q3: Why does Steven choose to have an extreme commute?___
A. Because gas prices are not high .
B. Because the commute is not tiring .
C. Because he can attend a better school .
D. Because he can have his favorite lifestyle .
【单选题】
Q4: Which of the following is the disadvantage of long commutes?___
A. Traffic jams .
B. Expensive housing .
C. Poorer life quality .
D. A tiring and boring trip .
【单选题】
Q1: What did Katy like about Jason’s last Halloween party?___
A. She liked playing an interesting game .
B. She enjoyed seeing many of her old friends .
C. She enjoyed wearing her Halloween costume .
D. She liked the decorations in Jason's front yard .
【单选题】
Q2: What is the actual reason that Katy doesn’t want to attend Jason’s party?___
A. None of her friends likes Jason .
B. None of Jason's guests is young .
C. She wants to go to Linda's party ..
D. She went to Jason's party last year .
【单选题】
Q3: What is special about Linda’s party?___
A. The party will last four hours .
B. Six people will attend the party .
C. They will have huge bags of candy .
D. They will play a new game called "GuessWho ".
【单选题】
Q4: What will Katy do to solve her problem?___
A. Go to Jason's party .
B. Go to Linda's party .
C. Attend both Jason's and Linda's parties .
D. Celebrate Halloween with her parents .
【单选题】
Q1: What is special about this year’s Black Friday shopping?___
A. Some stores offered bigger holiday discounts .
B. Some stores provided more choices of nightlife.
C. Some stores made efforts to attract young people .
D. Some stores opened much earlier than they used to .
【单选题】
Q2: Why did some stores open at midnight on Thanksgiving night?___
A. To attract young customers .
B. To beat other stores for sale.
C. To let people sleep late the next day .
D. To keep people stay up for the night .
【单选题】
Q3: How many Black Friday shoppers were reported to go to the shops at midnight this year?___
A. 24 percent .
B. 37 percent .
C. 9.5 percent .
D. 23.5 percent .
【单选题】
Q4: What can we learn about the 15-year-old Jenny?___
A. She and her cousins went back home at midnight .
B. She liked the traditional 4 a.m. Black Friday.
C. She preferred midnight shopping to early morning shopping .
D. She and her cousins got up very early to buy discounted items .
【单选题】
Q1: Why did the woman decide to do a triathlon?___
A. Because she did it in college .
B. Because she wanted to be tough .
C. Because her sister did it and liked it .
D. Because her sister said it was good for her .
【单选题】
Q2: When did the man first do a triathlon?___
A. Last year .
B. In college .
C. Last week .
D. In high school .
【单选题】
Q3: How does the man feel about running?___
A. Boring.
B. Scaring .
C. Exciting .
D. Interesting .
【单选题】
Q4: Why doesn’t the woman like swimming in the triathlon?___
A. Because she fears that a big fish might eat her .
B. Because she fears that she would get lost in lakes .
C. Because she doesn't want to scare away small fishes .
D. Because she doesn't like swimming with many people .
【单选题】
Q1: What is the ratio of positive to negative emotions that can make a person happier?___
A. 1:3.
B. 3 :1.
C. 1 :10 .
D. 10 :1.
【单选题】
Q2: What is the most exciting finding about increasing positive emotions?___
A. It improves relationships .
B. It leads to greater success .
C. It helps develop creativity .
D. It contributes to good health .
【单选题】
Q3: What does the speaker say about negative feelings?___
A. People should turn every negative feeling around .
B. Negative feelings can sometimes have positive effects .
C. Negative feelings often cause people to make mistakes .
D. People should never show negative feelings in public places .
【单选题】
Q4: What is the main idea of the passage?___
A. People should learn to manage their emotions .
B. People should be patient with their negative feelings .
C. People should learn to analyze causes of unhappiness .
D. People should identify as many positive feelings as possible .
