问题 问答题

某同学家有一台电热水器,部分铭牌如下,根据铭牌所提供的信息,求:

(1)热水器储满水时所装水的质量是多少?

(2)热水器正常工作时电流有多大?

(3)储满水的热水器要使水温从17℃升高到50℃,热水器的效率是90%,热水器正常工作需要多长时间?[C=4.2×103J/(kg•℃)]

额定电压220V  容积100L
额定功率2 200W频率50Hz

答案

(1)由铭牌提供数据容量为100L可知,V=100L=10dm3=0.1m3

由ρ=

m
V
得:

m=ρV=1.0×103kg/m3×0.1m3=100kg;

(2)根据P=UI可得:

热水器正常工作时的电流I=

P
U
=
2200W
220V
=10A;

(3)水吸收的热量:

Q=cm△t=4.2×103J/kg•℃×100kg×(50℃-17℃)=1.386×107J,

根据η=

Q
W
可得:

热水器消耗的电能W=

Q
η
=
1.386×107J
90%
=1.54×107J,

根据W=Pt可得:

t时间=

1.54×107J
2200W
=7×105s.

答:(1)热水器储满水时所装水的质量是100kg;

(2)热水器正常工作时电流有10A;

(3)热水器正常工作需要7×105s.

阅读理解

阅读理解。

     The reasons for a person's becoming an alcoholic have often been debated by psychologists and other

scientists. But recent studies suggest that the problem of alcoholism (酒精中毒) should also be the focus

of investigation by biologists.

     While such things as hard jobs, boredom, and unhappiness can lead to alcoholism, researchers at a

prominent university have found that there may also be a genetic factor involved in alcoholism. In the study,

children of alcoholic parents were surveyed. The result showed that the children of alcoholic parents were

more likely to become alcoholics themselves than were children of non-drinking parents.

     This evidence in itself is not conclusive (令人确信的) about anything. After all, it may be the constant

exposure (接触) and easy access to alcohol that cause the children of alcoholics to become alcoholics

themselves. But there is more evidence. The study found that children born of alcoholic parents but raised

by non-drinking foster (抚养的) parents also were susceptible to alcoholism. This group of offspring (后

代) was more likely to take up drinking than youngsters who were born of and raised by non-drinking

parents.

     Other evidence found in the study suggests that environment does not play as important a role in the

development of alcoholism as had been previously thought. The study found that the likelihood of alcoholism

was better predicted from the characteristics of the parents than from such environmental characteristics

as type of job or level of income.

1. What is the main point of the passage?

A. To describe the environment in the development of alcoholism.

B. To study the psychological factor in the development of alcoholism.

C. To describe how the children of alcoholic parents become alcoholics themselves.

D. To describe the close link between genetic make-up and alcoholism.

2. According to the passage, what can bring about alcoholism?

A. Biologists' investigation.

B. Non-drinking parents.

C. Hard jobs, boredom and unhappiness.

D. Foster parents' raising.

3. According to the findings of the study, who would be the most likely to become an alcoholic?

A. A person who had a hard job.

B. A person who was born of alcoholic parents.

C. A person who was raised by drinking foster parents.

D. A person who was born of and raised by non-drinking parents.

4. According to the passage, what should the problem of alcoholism be treated as?

A. A psychological problem.

B. An environmental problem.

C. A biological problem.

D. An educational problem.

单项选择题