【单选题】When a induction motor with 4 poles is supplied by 50Hz three-phase ac power source, the rated rotor speed is 1450r/min. The Slip of the induction motor is ( ).
【简答题】Listening and filling the blanks. Dialogue A Collecting the Laundry (G: Guest 客人 R : Room Attendant 客房服务员 ) R: Good morning , sir . Do you have ____ 1 ____ ? G: Yes , here you are . R: One __...