题目

如图甲所示的电路中，R1为滑动变阻器，R0、R2均为定值电阻，电源两端电压保持不变．改变滑动变阻器R1的滑片位置，两电压表的实数随电流变化的图线分别画在图乙所示的坐标系中．根据以上条件可知电阻R0的组织为            Ω，电源电压          V． 答案：       解：因为V1测量R1和R2两端的电压，V2测量R2两端的电压，所以从图象上可以读出：U1=10V，I1=1A，U1′=4V，I1′=4A； 所以列出的关系式为：U=10V+1A×R0 U=4V+4A×R0 解得：R0=2Ω U=12V． 故答案为：2Ω--- Do you know the reason _________ pilots turn off the plane’s lights before taking off?    ---The practice is for the passengers to adjust to the dark _________ an emergency. A. why; for fear that                    B. for which; in case of           C. how; for fear of                      D. that; in case