旋转变压器的主要用途是()。 ["A、输出电力传送电能","B、变压变流","C、调节电机转速","D、作自动控制系统中的随动系统和解算装置A、输出电力传送电能","B、变压变流","C、调节电机转速","D、作自动控制系统中的随动系统和解算装置"]
真空的磁导率为() ["A、210-7H/m","B、310-7H/m","C、410-7H/m","D、510-7H/m"]
下列对咽旁隙位置的描述,正确的是:() ["A.位于咽后隙的两侧","B.上至颅底,下达舌骨","C.内侧与咽缩肌及扁桃体相邻","D.外侧有腮腺及翼外肌","E.可分为前、后两隙"]
展线
用来描述物质导磁能力强弱的物理量是()。 ["A.电阻率","B.电导率","C.磁导率","D.磁阻"]
初测