为确保安全,在再生制动时,电动机应在()部电阻全部切除的情况下工作.
A.外
B.内
参考答案:C
My father served in the army in when he was in .
A.1950s; twenties
B.the 1950s; his twenties
C.the 1950s; the twenties
D.1950s; the twenties
NPN型晶体管处于放大工作状态时,总是( )。
A.发射极加正向电压,集电结加反向电压
B.发射极加反向电压,集电结加正向电压
C.发射极加正向电压,集电结加正向电压
D.发射极加反向电压,集电结加反向电压