问题 选择题

在如图所示的电路中,电源电压保持不变。闭合开关S后,向右移动滑片P。下列说法中正确的是(   )

A.电压表的示数变大

B.电压表的示数变小

C.电流表A的示数变大

D.电流表的示数变小

答案

答案:D

题目分析:由图可知,两电阻并联,电压表测电源的电压,电流表A1测干路的电流,电流表A测滑动变阻器R1的电流。闭合开关S后,向右移动滑片P,滑动变阻器R1的阻值增大,通过滑动变阻器R1的电流变小,干路的电流变小,即电流表A的示数变小,电流表A1的示数变小,电压表的示数不变。故选D

填空题
完形填空
完形填空。
     Being alone in outer space can be frightening. That is one reason why astronauts on solo (单独的) space
flights are given plenty of work to keep them   1   . There are also constant communications with people on
the earth.    2  , being with people from whom you cannot get away might be even harder than being   3   .
This is what happens on long submarine (潜水艇) voyages. It will also happen on   4   space flights in the
future. Will there be special problem of adjustment (调整) under such   5   ?
     Scientists have studied the reactions (反应) of men to one another during long submarine   6  . They have
found that the longer the voyage   7  , the more serious the problem of   8   is. When men are   9   together for
a long period, they begin to feel uneasy. Everyone has little habits of speaking and behaving that are ordinarily
acceptable. In the limited space over a long period of time, however, these little habits may become very   10   .
     Although no one wants to be  11  all the time, everyone needs some degree of privacy(隐私). When people
are enclosed together, they are in what is called a stress situation. That means that they are under an unusual
amount of   12    or stress.
     People who are well-adjusted are able to   13   stress situations better than others. That is one reason why
so much   14   is taken in choosing our astronauts. These men undergo (经历) a long period of  15  and
training. One of the things tested is their behavior under stress.
( )1. A. tired   
( )2. A. So far   
( )3. A. alone    
( )4. A. long     
( )5. A. cases    
( )6. A. trips    
( )7. A. goes     
( )8. A. gas     
( )9. A. shut up 
( )10. A. pleasing 
( )11. A. noisy    
( )12. A. pleasure 
( )13. A. deal with
( )14. A. care   
( )15. A. checking
B. asleep         
B. After all     
B. lonely         
B. fast           
B. situations     
B. travels         
B. lasts          
B. entertainment  
B. held up       
B. annoying       
B. alone         
B. conflict       
B. create         
B. trouble       
B. observing    
C. awake      
C. However    
C. loneliness  
C. dangerous  
C. degrees     
C. voyages     
C. spends      
C. adjustment  
C. brought up  
C. frightening 
C. personal    
C. power      
C. affect      
C. effort      
C. testing     
D. busy             
D. Therefore      
D. off              
D. direct         
D. conditions       
D. visits           
D. costs            
D. health           
D. picked up        
D. amazing          
D. single           
D. pressure         
D. work with        
D. notice           
D. examining