问题 选择题

如图所示,一圆柱形铁芯上沿轴线方向绕有矩形线圈,铁芯与磁极的缝隙间形成了辐向均匀磁场,磁场的中心与铁芯的轴线重合.当铁芯绕轴线以角速度ω沿顺时针方向匀速转动时,下列线圈中电流随时间变化的图象,正确的是(从图位置开始计时,NS极间缝隙的宽度不计,以a边的电流进入纸面,b边的电流出纸面为正方向)(   )

答案

D

题目分析:由于磁场是均匀的伏向分布,因此a、b边切割磁感线的有效长度不变,产生的是直流电,AB错;a边向右切割磁感线,由右手定则可知感应电流垂直纸面向外,为负方向,b边产生的感应电流垂直纸面向外,为负方向,D对;C错;故选D

点评:本题难度较小,注意磁场的分布特点是关键,在任何一个位置,穿过线圈的磁通量不发生变化,只是两个边在做切割磁感线运动

阅读理解

阅读表达。

      It is generally believed that nowadays young people lack the manners that their parents' generation

expects them to have. Although it is true that there is a difference in the generations,I do not believe that

it is fair'to say that today'syouths have bad manners.

     In the first place,the fact that young people do not always shake hands only reflects a move away from

the formali-ties( 礼节)  of the past.  It does not show lack of respect,but simply the present trend towards more relaxed social com-

munication.  Similarly,the way that we speak to each other is surely a manner of personal choice.  Even

though we maynot greet each other formally,this has nothing to do with manners. Youngsters have simply

developed their own greet-ings.

      Furthermore , I strongly oppose the opinion that young people are impolite and show lack of

consideration of others._____,most young people have perfect manners.  Naturally,there are always

exceptions( 例外).  Even older mem-bers of society can be ill-mannered at times.

      As far as I am concemed,the complaints about young people today are entirely without foundation.

Although thereare different attitudes towards manners in the generations,that shouldn't be considered as

rudeness. I suppose that any-one who says such things has not really tried to speak to the young

generation. If he or she did,I am sure they wouldfind that we are just like everyone else.

       To conclude,I think people wrongly regard the lack of formality as bad manners.  After all,

youngsters follow exam-ples set by others,so maybe the world around us has become less formal.

1.  What does the author think of the idea about youth's manners ? ( no more than 15 words)

   ____________________________________________________________________

2. Which sentence in the text is closest in meaning to the following one?

Even old generation in the society sometimes would manner impolitely.

____________________________________________________________________

3.  Fill in the blank in Paragraph 3 with proper words.

   ____________________________________________________________________

 4.  Why do the young not always shake hands when they meet each other? ( no more than 10 words)

   ____________________________________________________________________

5. Translate the underlined sentence in the fourth paragraph into Chinese.

   ____________________________________________________________________

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