初三物理热学电热器中有两根电阻丝,当其中一根单独通电时,可使电热器中的水10分钟沸腾,当另一根单独通电时,可使同样多的水

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  • W=U^2/R1*10min=U^2/R2*20min

    化简得:R2=2R1

    串联:R总=3R1

    W=U^2/R1*10min=U^2/R总*t

    10/R1=t/3R1

    得t=30min

    并联:R总=(U1*U2)/U1+U2=2/3R1

    W=U^2/R1*10min=U^2/(2/3)R*t

    t=20/3min

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