...ield 1.9.1 Vector Line of a Vector Field 矢量线的疏密表征矢量场的大小 例如：电场中的电力线 ( electric lines of force )，磁 场中的磁力线 ( magnetic lines of force ) 矢量线上每一点的切线方向代表该处矢量场的方向 ...
The existenceof electric currentin the conductor(notclosed)which is cut-ting the magnetic linesof force(B-lines) variably in the magnetic field is pointed out, and the acceleration isdiscussed.