如图所示的电路，电源电压恒定，R1=R2=6欧姆，当开关S1,S2都断开时，电流表的示数为0.5A

（1）S1S2断开，R1R2串联，U=I(R1+R2)=0.5*12=6V(2)S1S2闭合，R2短路，R1R3并联。I （1）S1S2断开，R1R2串联，U=I(R1+R2)=0.5*12=6V
(2)S1S2闭合，R2短路，R1R3并联。I1=6V/6=1A,I3=1.5A-1A=0.5A,R3=6V/0.5A=12（伏磨瞎1）S1S2断开，R1R2串联游梁，U=I(R1+R2)=0.5*12=6V(2)S1S2闭合，R2短路，R1R3并联。I1=6V/6=1A,I3=1.5A-1A=0.5A,R3=6V/缺空0.5A=12欧（3）P=UI=6V*1.5A=9W
（3）P=UI=6V*1.5A=9W

（1）S1S2断开，漏伏R1R2串联卜汪，U=I(R1+R2)=0.5*12=6V(2)S1S2闭合，R2短路，R1R3并返弊携联。I1=6V/6=1A,I3=1.5A-1A=0.5A,R3=6V/0.5A=12欧（3）P=UI=6V*1.5A=9W