题目

Just be happy. Sounds too simplistic, doesn’t it ? But, in reality, we can have much more happiness if we choose to consider things from a positive point of view. Everyone experiences the ups and downs of life, however, we can make a decision to take advantage of the negative or practice what the old saying says to do :“ When life gives you lemons, make lemonade!” It really boils down to your attitude and you have the ability to work your attitude into any shape you like. Here are some tips: l         Ignore those who tell you life is too difficult to be happy. What do t有一根细长而均匀的金属管线样品，横截面如图甲所示．此金属管线长约30cm，电阻约10Ω．已知这种金属的电阻率为ρ，因管内中空部分截面积形状不规则，无法直接测量，请你设计一个实验方案，测量中空部分的截面积S0，现有如下器材可选：A．毫米刻度尺B．螺旋测微器c．电流表Al（600mA，1.0Ω）D．电流表A2（3A，0.1Ω）E．电压表V（3V，6KΩ）F．滑动变阻器R1（2KΩ，O．5A）G．滑动变阻器R2（10Ω，2A）H．蓄电池E（6V，O．05Ω ）I．开关一个，带夹子的导线若干（1）上列器材中，应选用的器材有______（只填代号字母）．（2）在上面方框中画出你所设计的电路图，并把图乙的实物连成实际测量电路，要求尽可能测出多组有关数值．（3）实验中要测量的物理量有：______，计算金属管线内部空问截面积S的表达式为：S=______．