R1=12V÷0.2A=60Ω
R2=R×R1÷(R1-R)=20×60÷(60-20)Ω=30Ω
R1电能:U×I×t=12V×0.2A×10MIN÷60MIN/H=0.4WH
R2电能:U×I×t=12V×12V÷30Ω×10MIN÷60MIN/H=0.8WH
总电能:U×I×t=12V×12V÷20Ω×10MIN÷60MIN/H=1.2WH
也可以:0.4WH+0.8WH=1.2WH
R1=12V÷0.2A=60Ω
R2=R×R1÷(R1-R)=20×60÷(60-20)Ω=30Ω
R1电能:U×I×t=12V×0.2A×10MIN÷60MIN/H=0.4WH
R2电能:U×I×t=12V×12V÷30Ω×10MIN÷60MIN/H=0.8WH
总电能:U×I×t=12V×12V÷20Ω×10MIN÷60MIN/H=1.2WH
也可以:0.4WH+0.8WH=1.2WH