问题 问答题 简答题

蓄电池分哪几大类?简述蓄电池的结构及在主型机车上的用途。

答案

参考答案:

蓄电池分酸性蓄电池和碱性蓄电池两大类。

蓄电池由正极、负极、电解质、隔膜和容器五个主要部分组成。电池的正极活性物质通常是用各种金属氧化物、卤及卤化物、氧或含氧酸盐等,负极活性物质则用各种电位较负的金属或氢。电解质溶液采用酸、碱和盐的水溶液,隔膜的作用是把正、负极分隔开,防止发生短路现象。

蓄电池的用途可说出它在自己熟悉机车上的用途:如稳压、启机、供电给小升弓压缩机以及故障供电等。

阅读理解

Healthy people with stressful jobs who work long hours but get little satisfaction from what they do have twice the risk of dying from heart disease as satisfied employees, according to a study. Job stress has been known to cause heart problems in people who already have cardiovascular disease (心血管病). Finnish scientists have now shown that even in healthy people the pressures of work can take their toll. High blood pressure, lack of exercise, smoking and being overweight contribute to heart disease—a leading killer in many industrialized countries.

But Mika Kivimaki, of the Finnish Institute of Occupational Health, and his colleagues, who studied the medical histories of 812 healthy Finnish men and women in a metal industry company over 25 years, said job stress also plays an important role.

Workers who had the highest job-related stress levels at the start of the study were more than twice as likely to die of heart disease, according to the study published in The British Medical Journal. Work stress involves too much work as well as a lack of satisfaction and feeling undervalued and unappreciated. Many people work long hours but if the effort is rewarding the stress is minimized.

The British Heart Foundation said the results support earlier research showing that people in jobs with low control, such as manual(体力的) workers, could be as great risk of heart disease than other employees. “ It is advisable for people to try to minimize levels of stress at work and for employees to allow people to have more control at work and to be rewarded for their successes,” the foundation said in a statement.

小题1:Healthy people may die from heart disease of ____________.

A.too much job stress

B.working too hard

C.feeling valued

D.being satisfied小题2:Which one of the following is NOT right according to this passage?

A.High blood pressure is likely to cause heart disease.

B.Being overweight may cause heart disease.

C.Job stress is most likely to cause heart disease.

D.Working long hours must cause heart disease.小题3:The underlined word “minimized” in the third paragraph means “_________”.

A.increased

B.reduced

C.raised

D.cured小题4:The author’s purpose in writing the passage is to _________.

A.advise people not to work long hours

B.suggest that everyone be satisfied with everything

C.ask us to learn to enjoy ourselves

D.tell us that job stress threatens our health nowadays.

单项选择题