依P=U^2/R
R1=2.5^2/1=6.25欧姆
R2=2.5^2/0.8=7.8125欧姆
U1/U2=R1/R2=6.25欧姆/7.8125欧姆=4/5
依p=I^2*R
串联电流相等.
P1/P2=R1/R2=U1/U2=4/5