在磁铁或通电导线的周围空间都存在磁场,对置于其中的通电导线都有力的作用,可使通电导线发生转动,随着转动角度的增大,相互间的吸引力也增大,使彼此靠近.例1 如图1,将一通电导线放在一蹄形磁铁的正上方,导线可以自由移动,当导线通过如 A magnetic field exists in the surrounding space of the magnet or the current-carrying wire, and has a force effect on the current-carrying wire placed therein, so that the current-carrying wire rotates. With the increase of the rotation angle, the mutual attraction force also increases, so that they are close to each other. Example 1 As shown in Fig. 1, an energized wire is placed directly above a shoe magnet and the wire can move freely when the wire passes through