问题 选择题

如图所示,一电子束沿图中箭头所示方向通过两磁极间时,其偏转方向为(  )

A.向上

B.向下

C.向N极

D.向S极

答案

由图可知在磁铁外部,磁场方向从N极指向S极,根据左手定则有,让四指指向与电子束的运动方向相同,让磁感线穿过手心,根据大拇指的指向即可判断出洛伦兹力的方向,由此可知洛伦兹力的方向向下,故B正确,ACD错误.

故选B.

阅读理解

One morning, a blind boy sat on the steps of a building with a hat by his feet .He held a sign which said,“I am blind. Please help me.”

There were only a few coins(硬币) in the hat. A man was walking by. He took out a few coins from his pocket and dropped them into the hat .He then took the sign, turned it around, and wrote some words on it. He put the sign back so that everyone who walked by could see the new words.

Soon the hat began to fill up. A lot more people were giving money to the blind boy. That afternoon the man who had changed the sign came to see how things were. The boy recognized his footsteps and ask,“Are you the one who changed my sign in the morning? What did you write?”

The man said,“I only wrote the truth. I said what you said, but in a different way.”

What he had written was,“Today is a beautiful day, but I can’t see it.”

Do you think the first sign and the second sign were saying the same thing?

Of course both signs told people the boy was blind. But the first sign simply told people to help by putting some money in the hat. The second sign told people that they were able to enjoy the beauty of the day, but the boy could not enjoy it because he was blind.

The first sign simply said the boy was blind, while the second sign told people they were so lucky that they were not blind.

There are at least two lessons we can learn from this simple story.

The first is: Treasure(珍惜)what you have. Someone else has less. Try your best to help those who need your help.

The second is: Be creative. Think differently. There is always a better way.

小题1: From the passage we know that______.

A.the boy is the man’s son.

B.the man is one of his neighbors.

C.the boy is blind and needs help.

D.the boy works for the man.小题2: On the sign what the man wrote was,“_______.”

A.Treasure what we have already had.

B.Today is a beautiful day, but I can’t see it.

C.We are so lucky that we are not blind.

D.Try your best to help those who need your help.小题3:According to the passage, which of the following is TRUE?

A.The hat began to fill up after the man wrote some words on the sign.

B.The man took away all the few coins from the hat.

C.The boy wanted to get enough money to go to school.

D.Nobody wanted to give any coins to the blind boy.小题4:The word“recognized”here in Chinese means______.

A.承认

B.接受

C.表扬

D.认出小题5:“____”is the best title for this story.

A.Be careful.

B.Be creative. There is always a better way!

C.Be kind to the blind!

D.Do not always get, but offer!

单项选择题