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Parents often ______ their children______ some good living conditions.
家用电水杯利用了电流的____ 效应.某型号电水杯铭牌标有“220V 400W”字样,它正常工作时,发热元件的阻值为____ Ω.正常工作5分钟,电水杯消耗的电能为____ J.