说明：  2.1 预习 点电荷电场分布 2.2 实验一 电偶极子电场分布仿真 2.3 实验二 特殊边界条件的电场分布 2.4 实验三 直导线的磁场分布 2.5 实验四 磁偶极子的磁场分布
(2.1 preview point charge electric field distribution 2.2 experimental electric dipole electric field distribution simulation The distribution of electric field in 2.3 experiment two special boundary conditions The magnetic field distribution of 2.4 experiment three straight wire 2.5 the magnetic field distribution of the four magnetic dipoles)