问题 完形填空
完形填空。
     Breakfast is very important. It is one of   1   of the day. To keep healthy, everyone should   2   a
good breakfast .   3   the right food is necessary for good health . We way have eggs, bread, milk, etc.
(等等)  4   breakfast .
     Many students go to school without breakfast   5   they get up late or their parents don't cook for
them . It's   6   for their health. 
       7   breakfast children may not grow fast and may not study and play very well at school. They may
  8  . And when they're ill, they will   9   a long time in recovering (恢复).
      I think everyone should have some good   10   habits .
( )1. A. important 
                meals
( )2. A. to have     
( )3. A. Eating     
( )4. A. in       
( )5. A. why       
( )6. A. good     
( )7. A. Without     
( )8. A. is ill   
( )9. A. spend       
( )10. A. health     
B. the most important
     meals
B. having               
B. To eating           
B. with               
B. because             
B. nothing             
B. With                 
B. ill               
B. take               
B. healthy             
C. the most important
    meal
C. have                 
C. Eats               
C. on                 
C. so                 
C. bad                 
C. Under                 
C. are ill               
C. cost               
C. healthily             
D. most important
     meals
D. has                
D. Eat                
D. for                
D. but                
D. better              
D. No have            
D. be ill              
D. make                
D. bad                
答案

1-5    BCADB      6-10   CADAB

问答题

单位时间内流过管道横截面的液体体积叫做液体的体积流量(以下简称流量).由一种利用电磁原理测量非磁性导电液体(如自来水、啤酒等)流量的装置,称为电磁流量计.它主要由将流量转换为电压信号的传感器和显示仪表两部分组成.

传感器的结构如图所示,圆筒形测量管内壁绝缘,其上装有一对电极a和c,a,c间的距离等于测量管内径D,测量管的轴线与a、c的连接放像以及通过电线圈产生的磁场方向三者相互垂直.当导电液体流过测量管时,在电极a、c的间出现感应电东势E,并通过与电极连接的仪表显示出液体流量Q.设磁场均匀恒定,磁感应强度为B.

(1)已知D=0.40m,B=205×10-3T,Q=0.123/s,设液体在测量管内各处流速相同,试求E的大小(π去3.0)

(2)一新建供水站安装了电磁流量计,在向外供水时流量本应显示为正值.但实际显示却为负值.经检查,原因是误将测量管接反了,既液体由测量管出水口流入,从如水口流出.因为已加压充满管道.不便再将测量管拆下重装,请你提出使显示仪表的流量指示变为正直的简便方法;

(3)显示仪表相当于传感器的负载电阻,其阻值记为R.a、c间导电液体的电阻r随液体电阻率色变化而变化,从而会影响显示仪表的示数.试以E、R.r为参量,给出电极a、c间输出电压U的表达式,并说明怎样可以降低液体电阻率变化对显示仪表示数的影响.

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