题干

下面的图表是从某台电热饮水机说明书上收集到的信息.经分析得知,当开关S闭合时,饮水机处于加热状态,S断开时,饮水机处于保温状态.为了测量它加热时的实际功率,小明断开其它所有用电器,只将该饮水机接入家庭电路中,闭合开关S,测得热水箱中的水从20℃升高到100℃,所用时间为7.5min,同时观察到家中标有“1200r/kW•h”字样的电能表转盘转过120转.不考虑温度对阻值的影响[c=4.2×103J/(kg•℃)].根据以上信息,求:

热水箱容量

1L

额定电压

220V

加热时额定功率

880W

(1)饮水机热水箱中的水从20℃升高到100℃时所吸收的热量;

(2)饮水机在加热过程中的热效率;

(3)饮水机加热时的实际电压.

上一题 下一题 0.0难度 选择题 更新时间:2015-03-12 06:24:30

答案(点此获取答案解析)

解:(1)饮水机热水箱中水的体积:V=1L=1dm3=103m3,由ρ=
m
v
可得,水的质量:m=ρV=1.0×103kg/m3×103m3

同类题3

阅读理解

    Mick Polly,an owner of a toy store,lives with his teenage daughter Carolina in Kentucky.He is known as the Bike Man.Over the past five years,Mick has built hundreds of bikes for needy kids.

    One day in 2012,a 13﹣year﹣old boy with a broken bike walked by Mick's house."I was working in my garage(车库),and he asked if I could fix it,"says Mick,now 53.

    The boy's bike had a broken wheel.Mick sent a post(帖子) on Facebook,asking his friends if they had the needed part.One friend saw the post and gave away two used bikes.Mick took parts from each to build a new set of wheels for the boy.

    Soon after,Mick repaired a bike for the boy's brother and fixed one for his sister.Word spread,and during the year,he had fixed up lots of bikes for local kids whose parents were not able to afford new ones

    "People are throwing away bikes day and night,"says Mick.

    Mick puts the bikes and bike parts in his garage."I take off the good tires or the handlebars or the seats and use them,"he says.

    Up to now,the bike man has repaired hundreds of bikes and given away nearly 700newly repaired bikes.They're free,but the kids must agree to two things:They have to learn how to put waste things to good use and they have to try their best to study in school.

    If a kid's grades are low,Mick requires a teacher's note"saying that you're doing your best,"Mick says.Mick also hopes the bikes will get kids off the sofa."When I was growing up,we all rode our bikes,"he says."Hopefully these kids can get some exercise."