问题 问答题 简答题

电涌保护器能否限制操作过电压(电涌)?

答案

参考答案:

据美国和德国的研究,大部分操作过电压(电涌)的电压峰值不高(多数在3kV左右,很少会超过6kV),能量没有雷电电涌大。所以,能够限制雷电电涌的SPD,一般都能限制大部分操作过电压(电涌)。但是在靠近电气设备操作十分频繁的地点(如电梯控制中心和有电容补偿的母线),应该提高其最大持续运行电压,至少要求Uc〉1.45Uo。

阅读理解

In February 2006, Lydia Angyiou and her two sons were walking through their village in northern Canada. The sound of children shouting made her turn around. To her horror, Lydia saw a 700-pound polar bear behind her eyeing her seven-year-old son. Getting between the bear and her child, Lydia yelled at the children to run away. She then began hitting and kicking the animal as hard as she could. A neighbor who heard all the noise came and shot the bear. But everyone agreed it was Lydia who had saved her children’s lives. A local policeman described it this way: “… I guess when your back is up against the wall, … we come up with super-human strength.”

Where does this “super-human strength”, courage and quick thinking come from? Experts say it comes from stress! In stressful situations, the body releases chemicals that prepare it to take action. These chemicals give people the speed and strength they need to fight danger or run away from it.

When we think of stress, we usually think of its negative effects. Studies, though, show that moderate levels of stress are actually helpful. In fact, the way we perform is usually affected by the amount of stress we feel.

Stress causes the brain to release adrenaline(肾上腺素) which in turn increases our energy and excitement. The chemical gives us clearer minds and helps us to do more. This is why some people say they work better under a deadline.

Adrenaline that is not released for long periods of time can cause us to increase and strengthen our abilities instead of weakening them. We sometimes turn out our very best work when we push ourselves to the limit. Stress can also make us more confident. Handling small amounts of stress now prepares us for handling serious situations in the future. Who knows? Today’s stress may even prepare for the next polar bear that comes along!

小题1:In the first paragraph, the case of Lydia Angyiou is mentioned to______.

A.introduce the topic to be followed

B.remind us of the unexpected danger of life

C.praise Lydia Angyiou for her bravery

D.show the importance of super-human strength小题2:What does the policeman probably mean by saying “your back is up against the wall”?

A.You are helped.

B.You are inspired.

C. You are confident.

D.You are cornered.小题3:What would be the best title for the passage?

A.Brave Mother

B.The Cause of Stress

C.The Benefit of Stress

D.Super-human Strength

单项选择题 B型题