问题 计算题

(10分)家用电磁炉以其高效、节能成为新一代智能灶具,小明在家中关闭其他所有用电器,在只有电磁炉正常工作的情况下.请你回答下列有关问题:

(1)1标准大气压下,锅内装有4.5L温度为20℃的水,给电磁炉通电把水加热到沸腾,水至少吸收多少热量?[水的密度为1.0×103kg/m3,水的比热容为4.2×103J/(kg•℃)]

(2)把上述水烧开用了20min.家中安装的标有“3000r/(kW•h)”的电能表转了1400圈,求该电磁炉的额定功率?

(3)此电磁炉烧水时的效率是多少?

答案

(1)1.512×106J;(2)1400W;(3)90%

题目分析:(1)水的质量为:

水吸收的热量为:

(2)把水烧开消耗的电能为:

电磁炉的额定功率为:

(3),电磁炉的效率为:

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In the following passage, there are 20 blanks representing the words that are missing from the context. You are to put back in each of the blanks the missing word. The time for this section is 20 minutes.
Where do you really come from And how did you get (1) where you live today DNA studies suggest that all humans today (2) from a group of African ancestors who—about 60,000 years ago— (3) a remarkable journey.
The Genographic Project is seeking to chart new (4) about the migratory history of the human species by (5) sophisticated laboratory and computer analysis of DNA contributed by hundreds of (6) of people from around the world. In this unprecedented and real-time (7) effort, the Genographic Project is closing the gaps of what science (8) today about mankind’s ancient migration stories.
The Genographic Project is a five-year (9) partnership led by National Geographic Explorer-in-Residence Dr. Spencer Wells. Dr. (10) and a team of renowned international scientists and IBM researchers, are (11) cutting-edge genetic and computational technologies to analyze historical patterns in DNA (12) participants around the world to better understand our human genetic roots. (13) three components of the project are: to gather field research data (14) collaboration with indigenous and traditional peoples around the world; to invite (15) general public to join the project by purchasing a Genographic Project Public Participation Kit; (16) to use proceeds from Genographic Public Participation Kit sales to further (17) research and the Genographic Legacy Fund which in (18) supports indigenous conservation and revitalization projects. The Project is anonymous, non-medical, (19) , non-profit and non-commercial and all results will be placed in the (20) domain following scientific peer publication.