题型:选择题 图1为测量电压表V内阻r的电路原理图.图中两个固定电阻的阻值均为R,S1、S2是开关,E是电源(内阻可忽略)小题1:按电路原理图将图2中的实物图连线; 小题2:开关S1保持断开,合上开关S2,此时电压表的读数为U1;再合上开关S1,电压表的读数变为U2,电压表内阻r=_______(用U1、U2和R表示). 查看答案
题型:选择题 In the city the old .[ ]A. take good care of B. are taken good care of C. is taken good care of D. are been taken good care of 查看答案