如图所示,电源电压不变,R3=2R2.当闭合开关1,断开开关2时,电阻1两端电压为10V;断开开关1,闭合开关2时,电阻
4个回答

U/(R1+R2)×R1=10

U/(R1+R3)×R1=8

(R1+R3)/(R1+R2)=5/4

R2=1/2R3代入:

4(R1+R3)=5(R1+1/2R3)

4R1+4R3=5R1+5/2R3

R1=3/2R3

R1:R3=3:2