题干

用电阻率为,横截面积为S的导线,绕成闭合的边长为a的正方形线圈n匝。将此线圈垂直于磁场方向放置,如图所示,由于磁场的均匀变化使线圈中的感应电流为I,方向如图中箭头所示,则此可知(   )

A:磁场是增强的,磁感强度变化率为aS/4I

B:磁场是减弱的,磁感强度变化率为4I/aS

C:磁场是增强的,磁感强度变化率为aS/I

D:磁场是减弱的,磁感强度变化率为I/aS

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答案(点此获取答案解析)

B

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阅读下面一首诗歌,完成小题。

莱蒙托夫

                                                                                             那大海上淡蓝色的云雾里

                                                                                             有一片孤帆儿在闪耀着白光!……

                                                                                             它寻求什么、在遥远的异地?

                                                                                             它抛下什么、在可爱的故乡?……


                                                                                             波涛在汹涌——海风在呼啸,

                                                                                             桅杆在弓起了腰轧轧地作响……

                                                                                             唉!它不是在寻求什么幸福,

                                                                                             也不是逃避幸福而奔向他方!


                                                                                            下面是比蓝天还清澄的碧波,

                                                                                            上面是金黄色的灿烂的阳光……

                                                                                             而它,不安的,在祈求风暴,

                                                                                             仿佛是在风暴中才有着安详!