Question

如图,R1=20欧,R2=20欧,当开关S1和S2均断开时,电压表的示数为6V,电流表A的示数为0.6A.

Answer 1

1.,当开关S1和S2均断开时,R1,R3串联

R3=U3/I=6/0.6=10欧

U=IR=I(R1+R3)=0.6*(20+10)=18V

2.

当S1,S2均闭合时,R3,电压表被短路,R1,R2并联

电压表为0.

I1=U/R1=18/20=0.9A

I2=U/R2=18/20=0.9A

I=I1+I2=0.9+0.9=1.8A

3.P2=I2^2R2=(0.9*0.9)*20=16.2W

W=UIt=18*1.8*60=1944J