# Electromagnetics doubt

1. Dec 14, 2013

### bhanesh

Why j.ds has ' closed integral ' on below equation

2. Dec 14, 2013

### phinds

It would probably be easier to tell if you posted the image right-side-up.

By the way, in English, what you have is not a "doubt", it is a question. See https://www.physicsforums.com/showthread.php?t=607274

3. Dec 14, 2013

### Shyan

I think this is some kind of continuity equation.Its considering a region of space with some charge inside it.Because charge can't be created or destroyed,the only thing which can cause the amount of charge to change is a current and so we should have a surface integral of current density.But because we're interested in a region of space,the surface is the one enclosing that region which is of course closed.