问题 实验题

要测量一个额定电压是3.8V的小灯泡的额定功率,估计小灯泡工作时的电阻约为10Ω。现有电流表、电压表、开关各一个,三个规格分别为“10Ω 1A”、“50Ω 0.5A”和“1kΩ 0.1A”的滑动变阻器,导线若干,电源(8V)一个。

(1)小星设计了如图甲所示的电路图,通过分析你认为小星应选用规格为________的滑动变阻器。

(2)请你根据图甲所示的电路图,用笔画线代替导线,将图乙中的器材连成实验电路(要求减小误差,导线不要交叉)。

(3)小星正确选择了滑动变阻器,按图连接好电路,闭合开关,发现灯泡不亮,电流表无示数,任意移动滑动变阻器的滑片,电压表示数不变(示数不为零)。具体原因是___________________

(4)小星排除故障后,继续实验。当电压表的示数为3.8V时,电流表的示数如图丙所示,则通过小灯泡的电流为_______A,该灯泡的额定功率是_______W。

答案

(1)50Ω 0.5A

(2)

(3)灯L断路(或答灯L没有接通;或答电流表、电压表在电路中的位置互换了)(合理即可)

(4)0.34; 1.29(或1.3)

完形填空
完形填空
     A man wanted to make an investment (投资). An idea struck him:"Why don't I plant a small mango
tree and enjoy the benefits when it grows into a big one?" So he went to the __1_, bought a small tree
and took it home. To the pride of his family, he _2_ it in the center of his __3_.
      He read everything about _4_ a mango tree. He got up early every morning, for he was determined
to supply the tree with all the necessary nutrients. He watered it, _5_ it with manure (粪肥), and took
good care of its leaves by removing those _6_ ones. He made sure the tree received enough care.
      Many times he sat and _7_ the beauty of the growing tree while dreaming about the _8_ mangoes
that the tree would _9_. His mind was always filled with the wish to taste the first fruit of the tree.
     Years went by  10  …now, he had a big tree with its leaves shining and healthy, its bark healthy and
hard. It was a big attraction   11   it decorated his whole garden.
     Then one day he noticed a small bud (花蕾), which in a couple of days grew into a beautiful  12  .
Now he could   13   wait for the fruit so he started to increase his supply of nutrients and care. Then one
day the tree let out its first product-a small green fruit. The man was so  14  .
     He waited for a few more weeks till the fruit grew in  15  . The day came when he decided to   16 
 the first fruit of the tree. He   17   the tree, picked the fruit and then came his  18  . The fruit was not like
what he expected. It was hard, big and round. He was puzzled. He was sad.
     Seeing this, his   19    came and asked him what happened. He told them that the fruit from his tree
was not what he wanted. When the neighbours heard this, they did not know whether to   20   or
comfort him, for what he planted years ago was not a mango tree. We can only reap (收获) what we
plant.
( )1. A. city        
( )2. A. grew        
( )3. A. garden      
( )4. A. buying      
( )5. A. decorated    
( )6. A. green        
( )7. A. admired      
( )8. A. beneficial  
( )9. A. bear        
( )10. A. immediately
( )11. A. because    
( )12. A. flower      
( )13. A. always      
( )14. A. greedy      
( )15. A. age        
( )16. A. observe    
( )17. A. climbed    
( )18. A. anxiety    
( )19. A. children    
( )20. A. complain    
B. farm      
B. moved      
B. house      
B. improving  
B. equipped  
B. red        
B. drew      
B. expensive  
B. burst      
B. quickly    
B. if        
B. fruit      
B. hardly    
B. happy      
B. length    
B. sell      
B. cut        
B. cheers    
B. friends    
B. laugh      
C. market          
C. planted        
C. village        
C. keeping        
C. served          
C. white          
C. greeted        
C. healthy        
C. deserve        
C. narrowly        
C. though          
C. leaf            
C. never          
C. nervous        
C. size            
C. steal          
C. hid            
C. disappointment  
C. neighbours      
C. motivate        
D. shop          
D. threw        
D. yard          
D. raising      
D. supplied      
D. yellow        
D. operated      
D. tasty        
D. make          
D. suddenly      
D. when          
D. nut          
D. strangely    
D. sad          
D. width        
D. taste        
D. killed        
D. opinion      
D. relatives    
D. support      
单项选择题