(1)硬度大;电能转化为机械能和内能
(2)
①Q 吸=cm(t﹣t 0)=4.2×10 3J/(kg·℃)×1.5kg×(100℃﹣15℃)=535500J
②15min=900s,2min=120s
电热器消耗电能为:W 1=P 1t 1=750W×900S=675000J
电机消耗电能为:W 2=P 2t 2=180W×120s=21600J
所以,整个过程消耗的电能为:W=W 1+W 2=675000J+21600J=696600J
(1)硬度大;电能转化为机械能和内能
(2)
①Q 吸=cm(t﹣t 0)=4.2×10 3J/(kg·℃)×1.5kg×(100℃﹣15℃)=535500J
②15min=900s,2min=120s
电热器消耗电能为:W 1=P 1t 1=750W×900S=675000J
电机消耗电能为:W 2=P 2t 2=180W×120s=21600J
所以,整个过程消耗的电能为:W=W 1+W 2=675000J+21600J=696600J