An electric line of force is also a closed line; it too forms a loop and returns on itself.

电力线也是一条封闭线；它形成一个圈，返回原处。

youdao

An electric line of force is also a closed line; it too forms a loop and returns on itself.

电力线也是一条封闭线；它形成一个圈，返回原处。

youdao