问题 计算题

家用电饭煲是利用电流的热效应来工作的,如图是某种型号电饭煲的简化电路。当温控开关S闭合时,电饭煲处于加热状态,此时若它两端的电压为220V,它的功率为1100W(不考虑温度对电阻值的影响)。则

(1)电饭褒在加热状态下工作0.lh,消耗的电能为多少KW•h?

(2)Ro的电阻为多少Ω?

(3)当温控开关S断开时,电饭煲的总功率与加热状态时相比,将如何变化?并请说明原因。

答案

(1)0.11KW•h    (2)44Ω

(3)开关断开时总功率变小。断开时Ro与R串联,总电阻增大,电源电压不变,总功率变小。

题目分析:(1)电饭褒在加热状态下功率是1100W,工作0.1h,消耗的电能。

(2)当温控开关S闭合时,将Ro单独接入电路,它的功率为1100W,将电功率公式变形得,

Ro的电阻

(3)开关断开时,Ro与R串联,电路的总电阻增大,电源电压不变,根据,电路的总功率减小。

多项选择题
完形填空
完形填空。

     On August 26, 1999, New York City was struck by a terrible rainstorm. The rain caused the streets   1   
and the subway system almost came to a stop.
     Unfortunately, this happened during the morning rush hour. Many people who were going to work were
   2    to go home. Some battled to   3   a taxi or to get on a bus. Still others faced the   4   bravely, walking
miles to get to work.
     I   5   to be one of people on the way to work that morning. I went from subway line to subway line only
 to find that most   6   had stopped. After making my way   7   crowds of people. I finally found a subway
line that was   8  . Unfortunately, there were so many people waiting to   9   the subway that I could not even
get down the stairs to the  10 . So I took the train going in the opposite direction, and then switched back to
the downtown train. Finally, after what seemed like forever, the train  11  my stop. Then I had to walk several
blocks in the increasingly heavy rain. When I got to my office, I was  12  through, exhausted and  13 .
     My co-workers and I spend most of the day drying off. When it was 5:00 pm, I was ready to go home. I
was about to turn off my computer  14  I received an email from Garth, my Director:
     I would like to thank all of you who made the effort and  15  reported to work. It is always reassuring (令
人欣慰), at times like these, when employees so clearly show their  16  to their jobs. Thank you.
     Garth's email was short, but I learned more from that  17  message than I ever did from a textbook. The
email taught me that a few words of  18  can make a big difference. The rainstorm and the traffic  19  had
made me tired and upset. But Garth's words immediately  20  me and put a smile back on my face.

( )1. A. break    
( )2. A. forced   
( )3. A. order    
( )4. A. climate  
( )5. A. used     
( )6. A. practice 
( )7. A. to       
( )8. A. operating
( )9. A. check    
( )10. A. street   
( )11. A. paused   
( )12. A. wet      
( )13. A. ashamed  
( )14. A. while    
( )15. A. hardly   
( )16. A. devotion 
( )17. A. accurate 
( )18. A. promise  
( )19. A. troubles 
( )20. A. corrected
B. flood      
B. refused    
B. pay        
B. scenery    
B. promised   
B. routine    
B. through    
B. cycling    
B. carry      
B. ground     
B. crossed    
B. weak       
B. discouraged  
B. when       
B. casually   
B. donation   
B. urgent     
B. appreciate 
B. signals    
B. supported  
C. sink        
C. adjusted    
C. call        
C. storm       
C. deserved    
C. process     
C. over        
C. turning   
C. find        
C. floor       
C. reached     
C. sick        
C. surprised   
C. where       
C. absolutely  
C. connection    
C. brief     
C. advice      
C. rules       
C. amazed    
D. crash    
D. gathered   
D. search   
D. burden    
D. happened             
D. service   
D. for       
D. rushing   
D. board     
D. platform  
D. parked    
D. hurt      
D. puzzled   
D. after     
D. eventually
D. reaction  
D. humorous  
D. guidance  
D. signs     
D. refreshed