如图所示,设R1=R2=R3=R4=R,求开关S闭合和断开时,A、B两端的电阻之比为_.

问题描述:

如图所示,设R1=R2=R3=R4=R,求开关S闭合和断开时,A、B两端的电阻之比为______.

开关闭合时,电路结构为:R4被短路,R1、R2、R3并联,AB端总电阻为RAB=13R开关断开时,电路结构为:R3、R4串联后再与R1、R2并联,R3、R4串联电阻为R34=2R,R1、R2并联电阻R12=12R,则AB端总电阻为RAB′=2R×12R2R+12...