题目

如图所示的电路中，R1＝10 Ω，R2＝20 Ω。闭合开关S后，电压表V1与V2示数之比为( ) A．3∶1                                                 B．3∶2 C．2∶1                                                 D．1∶1 答案：B 点拨：V1测总电压，V2测R2两端的电压，根据串联电路的分压规律，电压与电阻成正比，所以选B。________ there was a little trouble, but things soon were quiet. [　　] A．FirstB．At first C．First of allD．First thing