【判断题】【消耗次数:1】
起动直流电动机时,励磁回路应与电枢回路同时接入电源。
正确
错误
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相关题目
【单选题】 直流电动机起动时必须在电枢回路中串联起动电阻,原因是刚起动时 ________。
①  主磁通较弱
②  反电动势为零
③  瞬间高压
【判断题】 他励直流电动机采用电枢回路串电阻调速可以实现无级调速。
①  正确
②  错误
【单选题】 他励直流电动机保持额定电压及额定磁通不变,增大电枢回路电阻,负载转矩不变,与直接起动相比起动电流?
①  变大
②  变小
③  不变
④  都不是
【单选题】 他励直流电动机( ),不适合频繁起动的大、中型电动机
①  电枢回路串电阻起动
②  降压起动
③  直接起动
【判断题】 当他励直流电动机的电枢电压和磁通为额定值、电枢回路串接电阻时,电动机的机械特性称为固有机械特性。
①  正确
②  错误
【判断题】 直流电动机有他励和自励励磁方式吗?
①  正确
②  错误
【单选题】 他励直流电动机励磁回路中串有电阻时,在启动时应将电阻置于何值?
①  最大
②  最小
③  其他
④  都不是
【单选题】 并励直流电动机,当电源反接时,转速方向( )。
①  反向
②  不变
③  不确定
【判断题】 改变并励直流电动机电源的极性,电动机旋转方向反向。
①  正确
②  错误
【判断题】 在直流电动机的电枢回路中串联一只调速变阻器的调速方法,称为电枢回路串电阻调速法。
①  正确
②  错误
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【单选题】 Today, however, some new skyscrapers ____ up from the ground in long, wide, and curves.
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②  achieve
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【单选题】 Waiter: ___Customer: No, thank you. I have already known what to order.
①  Do you like this kind of dishes?
②  You are welcome to our restaurant. Take seat, please.
③  Would you like to see a menu?
④  Everybody! Order, please!
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①  changing ?
②  to be changed ?
③  to change ?
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【单选题】 We have studied English for only one year, ____ we can perform English short play already.?
①  for ?
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①  leading
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【单选题】 How can he ____if he is not ____?
①  listen--hearing
②  hear--listening
③  be listening--heard
④  be hearing--listened to
【单选题】 Lily: Hello, John! What was the weather like yesterday?John: ____
①  I like nice and bright weather.
②  You don’t like cold weather, do you?
③  That was a favorable weather.
④  Nice and bright, not too cold.
【单选题】 10. Far away around the corner I could see a small female ____advancing towards us.
①  body
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【单选题】 It is often more difficult to find trained men than ____ for scientific research.
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