江西永新县芦溪中学刘星同学问:“在做奥斯特实验时,要在通电导线下方放一个与导线平行的小磁针,小磁针为什么不可能与导线平行?”要回答这个问题,要先了解在载有电流的长直导线周围空间产生磁场的方向特点． Liu Xing, Luxi Middle School, Yongxin County, Jiangxi Province, asked: “When doing the Oster experiment, we need to put a small magnetic needle parallel to the wire under the energized wire. Why can’t the small magnetic needle be parallel to the wire?” To answer this question, It is necessary to first understand the characteristics of the direction of the magnetic field generated in the space surrounding the long straight wire carrying current.