I=U/R 电压相等 电流比I1:I2=R2:R1=3:1
P=U^2/R 电压相等 P1:P2=R2:R1=3:1
P=U^2/R=12*12/18
1MIN=30S
W=480J
P=I^2R
P1:P2=R1:R2=1:2