某微波炉功率为1000W,小明用该微波炉加热质量为300g,温度为20°C的水沸腾,用时2min,则此微波炉的效率为__

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  • 300g=0.2kg

    Q吸=MC(t-t1)=0.3kgX4.2X10^3J/(kg.℃)X(100℃-20℃)=100800J

    W总=pt=1000WX120S=120000J

    效率:100800/120000X100%=84%