①正常发光,P=100W,U=220V,P=U^2/R----------------R=U^2/P=48400/100=484Ω
②W=Pt,注意t=60s,W=100W*60S=6000J
③电压不变,R=440Ω,P=U^2/R=48400/440=110W
①正常发光,P=100W,U=220V,P=U^2/R----------------R=U^2/P=48400/100=484Ω
②W=Pt,注意t=60s,W=100W*60S=6000J
③电压不变,R=440Ω,P=U^2/R=48400/440=110W