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Nov25-12, 07:19 AM
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Quote Quote by Blastrix91 View Post
When you say div B = 0 mean that magnetic field lines only forms closed loops, is that in the moment a magnetic field begins and end (if that were to happen) there would be a change in what goes in in relation to what goes out and thus div B wouldn't be 0? That at least makes sense to me.

The B described in Biot Savarts law is the same that is described in div B = 0 right? So from a pure mathematical standpoint div B shouldn't be 0 if it is decreased by r^2 the further in the coordinate system you go. If you get what I'm saying?
The picture that you have in your head of this is not quite right. If the lines are diverging fast then the lines 'going in' will all be concentrated over a small area and the lines 'going out' will be spread out over a greater remaining area. Draw it on paper rather than seeing it in your head and it may make more sense..