将I=U/R代入P=UI 推导出:P=UU/R=IIR P=w/t 变形得出:w=Pt,将P=UI代入,推导出:w=UIt Q=IIRt,若Q=W,则推导出:Q=Pt=UIt, 将I=U/R代入,又推导出:Q=UUt/R
由I=U/R可推导出:U=IR R=U/I由P=UI可推导出:P=w/t=U的平方/R=I的平方×R由Q=I*I*RT可推导出:Q=U的平方/R再×T=W/t=UIT