计算题:一台四极异步电动机接在工频50Hz电源上,转子实际转速n=1440r/min,求该电机的转差率。
埋设在混凝土内的钢配管的外径不得超过混凝土厚度的() ["A.1/2;","1/3;","1/4;","1/5."]
利用通信卫星可以传输的信息有() ["电话","电报","图像","数据"]
LNA指的是() ["A.双工器","B.上下行转换器","C.高功率放大器","D.低噪声放大器"]
电线管路应尽量避免弯曲过多过急,埋设于地下或混凝土楼板内时,弯曲半径不应小于管子外径的()倍. ["6倍;","8倍;","10倍;","12倍."]
主、再热汽温的调整原则?(规程)