题目

在图9(a)所示的电路中，电源电压为6伏且保持不变．电阻R的阻值为30欧．闭合电键S，电流表的示数如图9(b)所示。    ①求通过电阻Rl的电流    ②求电阻R2的阻值③若一段时间内电流对电阻Rl做的功为30焦，求这段时间内电流对电阻R2做的功W2。  答案： 0.2A   10欧姆    90焦耳解析: 20、While staying in Scotland alone,          A loneliness was always around me      B many interesting places were visited. C I was a bit homesick                       D my friends in China encouraged me a lot