问题 选择题

如图,在虚线所围的矩形区域内,同时存在场强为E的匀强电场和磁感应强度为B的匀强磁场。已知从左方水平射入的电子,穿过该区域时未发生偏转,重力可忽略不计,则在这个区域中的E和B的方向不可能的是

A.E和B都沿水平方向,并与电子运动方向相同

B.E和B都沿水平方向,并与电子运动方向相反

C.E竖直向上,B垂直于纸面向外

D.E竖直向上,B垂直于纸面向里

答案

答案:D

题目分析:从左方水平射入的电子,穿过该区域时未发生偏转,说明电子所受的电场力与磁场力的合力不可能与v的方向不在同一直线上,在AB两个选项中,电子受到的磁场力为0,受到的电场力与电子运动方向在同一直线上;在C选项中,电子受到的合力为0;在D选项中,电子受到的合力方向向下,所以D是不可能的。

阅读理解

阅读理解。

     People usually hate mice, but people almost all over the world like one mouse-the famous Mickey

Mouse.

     Fifty years ago, most films had no sounds. A man called Walt Disney made a cartoom mouse. The

cartoon mouse could talk in these films. He named his mouse Mickey Mouse. Soon Mickey Mouse

became a good friend of both young and old people. Children liked to see their lovely friend, because he

brought happiness to them.

     Mickey is a clean mouse right from the beginning. Maybe this is why people love Mickey Mouse

very much. In his early life, Mickey did some wrong things. People were very angry. They wrote to

Disney and said they did not want Mickey to do wrong things. Because there were some things that

Mickey could not do, Disney made a new animal called Donald Duck. He also made a dog, Pluto. This

dog does some foolish and wrong things whenever he goes. Now our Mickey Mouse is more interesting

as well. He is known as a star of beauty and wisdom (智慧). He has his friends in almost every country.

1. Mickey Mouse first came out     _    .

A. on TV          

B. in the film    

C. in the play    

D. in a picture-book

2. Children love Mickey Mouse because _____.

A. it can speak      

B. it is clean    

C. it makes them happy  

D. it is a mouse

3. The dog, Pluto, is       _  .

A. a fool that often does something wrong

B. a clever dog that can do everything well

C. a beautiful dog that people like very much

D. a famous dog as a star of beauty and wisdom

问答题 简答题