题目内容


 “顿牟”指玳瑁的甲壳,“掇芥”的意思是吸引芥子之类的轻小的物体.不考虑万有引力的作用,发生“顿牟掇芥”时,两者可能的带电情况是(                                                                                                   )

    A. 玳瑁壳带正电,芥子带正电      B. 玳瑁壳带负电,芥子带负电

    C. 玳瑁壳带正电,芥子不带电      D.  玳瑁壳不带电,芥子不带电

                                                                                                                          

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以下是“描绘小灯泡的伏安特性曲线”实验的操作步骤:                                               

A.闭合电键,记下电流表、电压表的一组示数(I,U),移动变阻器的滑动触头位置,每移动一次记下一组(I,U)值,共测出12组左右的数据.                                                                                          

B.将电流表、电压表、变阻器、电灯、电源开关正确连成电路,电流表外接,变阻器采用分压式,如图所示                                                                                                                                        

C.调节触头位置,使闭合电键前触头处于变阻器的左端.                                        

D.按所测数据,在坐标纸上描点并将各点用直线段连结起来,得出小灯泡的伏安特性曲线.                                                                                                                                         

(1)以上各步骤中存在错误或不妥之处的是                                            ,应如何改正                 ?                        

(2)将步骤纠正后,按实验先后顺序排列起来                          .                             

                                                                                                         

                                                                                                                                  

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