Electric field lines of positive source charge end on ....?

1. Sep 11, 2015

gracy

I have read that electric field lines of positive source charge end on negative charge and Today I came to know that electric field lines of positive source charge end on infinity,which one is correct?I think electric field lines of positive source charge end on infinity if the positive source charge is isolated no negative or positive charges near it.And electric field lines of positive source charge end on negative charge if negative charge is in proximity or somewhere around the positive source charge.Right?

2. Sep 11, 2015

anorlunda

Yes, you are pretty much correct.

Another way to think of it, is that an isolated positive charge terminates on a hypothetical negative charge infinitely far away. Ditto for a negative charge.

By the way, that is one argument for charge conservation. If the positive charge were to suddenly disappear, so would the lines of field have to instantly dissapear infinitly far away. The change would have to propagate faster than light. But it can't propagate faster than light, so the charge cannot disappear.