问题 选择题

如图所示,电子射线管(A为其阴极),放在蹄形磁轶的N、S两极间,则荧光屏上的电子束运动径迹_________偏转。(填“向上”、“向下”“不”)。

答案

向下 

题目分析:因为A是阴极,B是阳极,所以电子在阴极管中的运动方向是A到B,产生的电流方向是B到A(注意是电子带负电),根据左手定则,四指指向A,手掌对向N极(就是这个角度看过去背向纸面向外),此时大拇指指向下面,所以轨迹向下偏转.

点评:伸开左手,使大拇指跟其余四个手指垂直,并且跟手掌在同一平面内,把手放入磁场中,让磁感线穿过掌心,四指所指为正电荷运动方向,拇指所指方向为电荷所受洛伦兹力的方向.(注:对负电荷而言,四指所指方向为其运动的反方向)

阅读理解

阅读理解。

     As the pace (节奏) of life continues to increase, we are fast losing the art of relaxation. Once you are

in the habit of rushing through life, being on the go from morning till night, it is hard to slow down. But

relaxation is essential for a healthy mind and body.

    Stress (压力) is a natural part of everyday life and there is no way to avoid it. In fact, it is not the bad

thing it is often supposed to be. A certain amount of stress is vital to provide motivation and give purpose

to life. It is only when the stress gets out of control that it can lead to poor performance and ill health.

     The amount of stress a person can withstand (承受) depends very much on the individual. Some

people are not afraid of stress, and such characters are obviously prime material for managerial

responsibilities, others lose heart at the first sign of unusual difficulties. When exposed to stress, in

whatever form, we react both chemically and physically. In fact we make choice between "flight or fight"

and in more primitive days the choices made the difference between life or death. The crises we meet

today are unlikely to be so extreme, but however little the stress, it involves the same response. It is when

such a reaction lasts long, through continued exposure to stress, that health becomes endangered. Since

we can't remove stress from our lives (it would be unwise to do so even if we could), we need to find

ways to deal with it.

1. People are finding less and less time for relaxing themselves because _____.

A. they regard working as their greatest enjoyment

B. they believe that work is superior to relaxation

C. they are traveling fast all the time

D. they are becoming busier with their work than ever before

2. According to the author, the most important character for a good manager is his _____.

A. strong will to withstand stress    

B. knowing the art of relaxation

C. high sense of responsibility      

D. having control over performance

3. Which of the following statements is TRUE, according to the passage?

A. We can find quite a few ways to avoid stress.

B. Stress is always harmful to people's health

C. It's easy to change the habit of keeping oneself busy with work.

D. Different people can bear different amount of stress.

4. In the last sentence of the passage, "do so" refers to _____.

A. "expose ourselves to stress"          

B. "find ways to deal with stress"

C. "remove stress from our lives"        

D. "establish links between diseases and stress"

5. According to the author, the right attitude toward stress is _____.

A. to avoid it                        

B. to try to deal with it

C. to regard it as a vital motivation      

D. to find some relaxation  

单项选择题 A1/A2型题