问题 问答题 简答题

为什么要在断电器触点旁并联一个电容器?

答案

参考答案:

在断电器触点旁并联一个电容器的原因是:在触点打开的瞬间,初级绕组中产生的自感电流与原电流方向相同,其电压高达300V左右,在断电器间产生强烈的火花。为了消除火花,故并联一个电容器

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     It amazed me-every time I saw Joe he was smiling. It didn't matter whether he had to   1   at a stop light,
or if he were the seventh person in   2   at the bank , and the teller closed her window just   3   he got there. Joe
always smiled. It made me wonder why he always seemed so   4  .
     Having observed Joe with other people, I also noticed something else. Joe   5   people how they were doing,
and really seemed to listen to their answers. He was   6   if someone was hurt , and had kind words, and   7   to
help in any way he could.
     It made me think… what if I tried to smile more? An   8   of sorts began when I went to a grocery store. I
   9   as I went up and down the aisles (过道)... and people I didn't even  10  smiled back at me. Some even
  11   ! The little kid in the cart who was giving his mother a  12  time saw me smile and stopped talking…and,
you guessed it-he made a little  13  attempt at a smile. The man in the handicapped cart  14   a person to reach
something… I could get that for him. The smile even  15  to him, and he thanked me and smiled at me.
     As I  16   home, I was smiling. I thought about what I had just  17  , and when someone passed my car and
gave me a gesture, I smiled at him. He looked  18  .
     Now I know a smile is a  19  thing, but what if we were all to try to smile a few more times each day? I
couldn't believe how great I felt.   20   in my life had changed-but maybe it had. For what I learned was that
such a small thing could lift not only my spirits, but those around me as well.
( )1. A. wait     
( )2. A. advance 
( )3. A. though  
( )4. A. patient  
( )5. A. asked   
( )6. A. angry   
( )7. A. agreed   
( )8. A. example 
( )9. A. sang     
( )10. A. welcome
( )11. A. spoke  
( )12. A. pleasant 
( )13. A. weak   
( )14. A. required 
( )15. A. spread 
( )16. A. learned  
( )17. A. faced   
( )18. A. scared  
( )19. A. funny   
( )20. A. Nothing 
B. suffer      
B. addition   
B. before      
B. active      
B. observed   
B. nervous    
B. offered    
B.  experiment 
B. nodded      
B. greet      
B. laughed    
B. hard        
B. polite      
B. demanded    
B. approached  
B. drove      
B. paid       
B. disappointed
B. worthy      
B. Everything  
C. look    
C. total   
C. while   
C. happy   
C. recorded  
C. fearful 
C. refused 
C. instance 
C. smiled   
C. recognize 
C. whispered 
C. smooth  
C. shy     
C. ordered  
C. advanced 
C. ran     
C. wasted   
C. puzzled 
C. valuable 
C. Something
D. slide       
D. line        
D. because     
D. wise        
D. allowed     
D. sympathetic 
D. used        
D. arrangement 
D. talked      
D. know        
D. shouted     
D. good        
D. sincere     
D. nee ded     
D. reached     
D. moved       
D. sacrificed  
D. annoyed     
D. small       
D. Anything    
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