问题 问答题 简答题

什么叫雷电的反击现象?如何消除反击现象?

答案

参考答案:

雷电的反击现象通常指遭受直击雷的金属体(包括接闪器、接地引下线和接地体),在接闪瞬间与大地间存在着很高的电压,这电压对与大地连接的其他金属物品发生放电(又叫闪络)的现象叫反击。此外,当雷击到树上时,树木上的高电压与它附近的房屋、金属物品之间也会发生反击。要消除反击现象,通常采取两种措施:一是作等电位连接,用金属导体将两个金属导体连接起来,使其接闪时电位相等;二是两者之间保持一定的距离。

阅读理解

Too many people want others to be their friends, but they don’t give friendship back. That is why some friendships don’t last very long. To have a friend, you must learn to treat your friend the way you want your friend to treat you. Learning to be a good friend means learning three rules: be honest; be generous (宽宏大量的);be understanding.

Honesty is where a good friendship starts. Friends must be able to trust one another. If you don’t tell the truth, people usually find out. If a friend finds out that you haven’t been honest, you may lose your friend’s trust. Good friends always count on one another to speak and act honestly.

Generosity means sharing and sharing makes a friendship grow. You don’t have to give your lunch money or your clothes, or enjoy, like your hobbies and your interests. Naturally you will want to share your ideas and feelings. These can be very valuable to a friend. They tell your friend what is important to you. By sharing them you help your friend know you better.

Sooner or later everyone needs understanding and help with a problem. Something may go wrong at school. Talking about the problem can make it easier to solve . Turning to a friend can be a first step in solving the problem. So to be a friend you must listen and understand. You must try to put yourself in your friend’s place so you can understand the problem better.

No two friendships are ever exactly alike (相同). But all true friendships have three things in common. If you plan to keep your friendships, you must practice honesty, generosity and understanding.

小题1:Some friendships don’t last very long because       .

A.there are too many people who want to make friends.

B.they don’t know friendship is something serious

C.they receive others’ friendships but never give others friendships

D.they always give other people friendships小题2:According to the passage , honesty is          .

A.as important as money

B.more important than anything else

C.something countable

D.the base of a friendship小题3:Which of the following is NOT true in the passage?

A.A friend who gives you his lunch money is a true friend.

B.Always tell your friend the truth.

C.Discussing your problems with your friend often helps to solve the problem.

D.Sharing your mind with your friend is of great value.小题4:The best title of this passage is        .

A.A Friend in Need Is a Friend Indeed

B.Honesty Is the Best Habit

C.How to Be a Friend

D.Three Important Points in Life

单项选择题