【单选题】The purpose of the DC generator brushes is to ___.
A.
neutralize armature reaction
B.
conduct electric current to an outside circuit
C.
convert DC current to AC current
D.
provide excitation to a DC generator
【单选题】Chattering of the collector ring brushes on a generator may be remedied by ______.
A.
lubricating brush holders
B.
re-insulating the brushes
C.
cleaning the collector rings
D.
increasing length of pigtail
【单选题】In a modern three-phase A.C. synchronous brushes generator, the excitation winding is on the rotor. That means . A.The generator need not excitation.
B.
The winding on the rotor is for inputting excitation current.
C.
There are three phase windings on the rotor.
D.
The generator has no brushes.
【简答题】(2r12?威海)六月,正是我市桃子成熟上市的时节.在你享受桃子的甘甜之时,是否知道桃树是怎样开花结实的呢?请据图回答下列问题. (1)“人间s月芳菲尽,山寺桃花始盛开”.这句诗反映出,影响桃树开花的非生物因素是______. (2)要观察桃花子房里面的胚珠,应采用的方法是______ A.用刀片横向剖开子房,用显微镜观察 B.用刀片横向剖开子房,用放大镜观察 C.用刀片纵向剖开子房,用放大镜观察...
【单选题】语言随着社会生活的变化而变化,语音、词汇和语法都会发生变异。其中,最活跃的是( )的变化。
【多选题】如果(F/P,12%,5)=1.7623,则下列等式正确的有( )
【单选题】语言随着社会生活的变化而变化,语音、词汇和语法都会发生变异。其中,最活跃的是()的变化。
【多选题】如果(F/P,12%,5)=1.7623,则下述系数正确的有
【多选题】一般而言,下列工艺过程属原料接收工序的为:( )
【单选题】(1分) 语言随着社会生活的变化而变化,语音、词汇和语法都会发生变异。其中,最活跃的是( )的变化。