一个家用电能表的盘面上标有“6400 r/kW·h”字样,若某个电热水器单独使用时,电表转盘在100s内转了220转,则
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消耗的电能:=220r ÷6400r/(kWh) = 220/6400 kWh = 0.034375 kWh = 123.75kJ

水的比热容是 4.2kJ/(kg℃)

Q=△m × Cp ×△T

△m = Q÷Cp÷△T

= 123.75 kJ ÷ 4.2kJ/(kg℃)÷ 10℃

= (123.75÷42) kg

= 2.946 kg