问题 问答题

某工厂设计了两种淋浴器,一种是淋浴时电流直接对流动的水加热;另一种则是备有水箱,待水箱中的水加热至合适的温度后再供淋浴,按一般淋浴要求:淋浴器水流量约为10L/min,合适的水温约50℃,用水时间约为5min,加热前的水温按20℃考虑,一般家庭供电电路允许的最大电流为20A.请根据以上情况和要求完成:

(1)按淋浴器用水的流量为10L/min,每分钟用水多少kg?

(2)电加热器的效率为70%,他一次淋浴约消耗多少电能?

(3)通过具体的计算,结合数据分析论证哪一种淋浴器不适合一般家庭选用?

答案

(1)淋浴器每分钟用水体积为:V=10L/min×1min=10L=10-2m3

用水质量为:m=ρV=1×103kg/m3×10-2m3=10 kg

答:淋浴器每分钟用水质量为10kg.

(2)一次淋浴需要5min,水从20℃升高到50℃需要吸收的热量为:Q=cm(t-t0)=4.2×103J/(kg•℃)×10kg×5×(50℃-20℃)=6.3×106J

因为电加热效率是70%,所以消耗的电能:W=

Q
η
=
6.3×106J
70%
=9×106J

答:一次淋浴约消耗电能是9×106J.

(3)若选用电流直接加热,按一次淋浴消耗电能约9×106J,而每次淋浴时间5min则电路提供的电功率为:P=

W
t
=
106J
5×60s
=30000W=30kW

一般家庭不可能达到30kW电功率,所以电流直接加热型电热淋浴器不适合.

完形填空
下面文章有5处需要添加小标题。请从以下选项(A、B、C、D、E和F)中选出符合各段意思的小标题,并在答题纸上将相应选项的标号涂黑。选项中有一项是多余选项。
A. There are few statues in the Middle East.
B. Art is a good means for people to know about religions.
C. Artists express their feelings and opinions in their works.
D. People know more about our culture through learning art history.
E. Art is more objective than history itself.
F. Art history provides information of different places and people.
小题1:                 
A study of art history might be a good way to learn more about a culture than is possible to learn in general history classes. Most typical history courses concentrate on politics, economics and war. But art history focuses on much more than this because art reflects not only the political values of a people, but also religious beliefs, emotions, and psychology.
小题2:                
In addition, information about the daily activities of our ancestors – or of people very different from our own – can be provided by art. In short, art expresses the essential qualities of a time and a place, and a study of it clearly offers us a deeper understanding than can be found in most history books.
小题3:                
In history books, objective information about the political life of a country is presented; that is, facts about politics are given, but opinions are not expressed. Art, on the other hand, is subjective: it reflects emotions and opinions. The great Spanish painter Francisco Goya was perhaps the first truly “political” artist. In his well-known painting The Third of May 1808, he criticized the Spanish government for its misuse of power over people. Over a hundred years later, symbolic images were used in Pablo Picasso’s Guernica to express the horror of war. Meanwhile, on another continent, the powerful paintings of Diego Rivera, Jose Clemente Orozco, and David Alfaro Siqueiros – as well as the works of Alfredo Ramos Martins – depicted these Mexican artists’ deep anger and sadness about social problems.
小题4:                
In the same way, art can reflect a culture’s religious beliefs. For hundreds of years in Europe, religious art was almost the only type of art that existed. Churches and other religious buildings were filled with paintings that depicted people and stories from the Bible. Although most people couldn’t read, they could still understand biblical stories in the pictures on church walls.
小题5:                
By contrast, one of the main characteristics of art in the Middle East was (and still is) its absence of human and animal images. This reflects the Islamic belief that statues are unholy. That’s why no figures can be found in or around places of interest in these regions.
选择题