如图所示，一水平放置的圆形通电线圈1固定，从上向下看，电流方_爱下问搜题

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问题选择题

如图所示，一水平放置的圆形通电线圈1固定，从上向下看，电流方向为逆时针方向，另一个较小的圆形线圈2从线圈1的正上方下落，在下落的过程中两线圈平面绐终保持平行且共轴，则线圈2从线圈1的正上方下落至线圈1的正下方的过程中（两线圈位于同一水平面位置除外），从上向下看线圈2，下列说法正确的是（　　）

A．线圈2始终有顺时针方向的感应电流

B．线圈2先有顺时针后有逆时针方向的感应电流

C．线圈2在线圈1的上、下两边的加速度都小于g

D．线圈2在上方有扩张趋势，在下方有收缩趋势

答案

A、在线圈1上方时，根据安培定则，知线圈1产生的磁场方向向上，通过线圈2的磁通量增加，根据楞次定律，感应电流的方向为顺时针方向．在线圈1下方时，通过线圈2的磁通量减小，根据楞次定律，感应电流的方向为逆时针方向．故A错误，B正确．

C、根据楞次定律的另一种表述：感应电流的效果总是反抗产生感应电流的原因．“来拒去留”、“增缩减扩”，知线圈2在线圈1的上、下两边的加速度都小于g．在线圈1上方，磁通量增加，线圈2有收缩趋势，在线圈1下方，磁通量减小．线圈2有扩张趋势．故C正确，D错误．

故选BC．

完形填空

Now that I am no longer young, I have friends whose mothers have passed away. I have heard these sons and daughters say they never fully appreciated their mothers ___小题1:___ it was too late to tell them. I am blessed (赐福) with the dear mother who is still alive. I ___小题2:___ her more each day. My mother does not change, but I ___小题3:___ . As I grow older and wiser, I realize ___小题4:___ an extraordinary person she is. How ___小题5:___ that I am unable to speak these words in her ___小题6:___ , but they flow easily from my pen.
　　How does a daughter begin to thank her mother for life itself? For the love, patience and just ___小题7:___ hard work that go into ___小题8:___ a child? For running after a toddler (学走步的小孩), for understanding a ___小题9:___ teenager, for tolerating (忍受;容忍) a college student who knows ___小题10:___ ? For waiting for the day when a daughter ___小题11:___ how wise her mother really is?
　　How does a ___小题12:___ woman thank a mother for ___小题13:___ to be a mother? For being ready ___小题14:___ advice (when asked) or remaining ___小题15:____ when it is most appreciated? For not saying, “I told you so,” when she could have uttered these words ___小题16:___ ? For being ___小题17:___ herself-loving, thoughtful, patient, and forgiving?
　　I don’t know how, dear God, except to ask you to bless her as richly as she ___小题18:___ and to help me live up to the example she has ___小题19:___ . I pray that I will look as good in the eyes of my children as my mother ___小题20:___ in mine.

小题25:A.sad B.glad C.comic D tragic

A．dozen times

B．a dozen of times

C．dozens of times

D．dozen of time

B．essentially

单项选择题 A1/A2型题

传染病病区内不属于污染区的是（）。

A.病室

B.患者浴室

C.厕所

D.病区走廊

E.门诊诊室