Fom gauss' law regarding magnetic fields, we have that magnetic flux is zero. But we do use (nonzero) magnetic flux to calculate other values, such as emf (faraday's law of induction). Can someone explain to me how magnetic flux can be both zero and have a value? Thanks!

Question

anonymous · Answer

Gauss' law does not say that the magnetic flux is zero, it says that the sum of the magnetic flux over a closed surface is zero.

Faraday's law is the sum of the magnetic flux through an open surface.

anonymous · Answer

By closed surface do you mean something like a box? And an open surface would be a 2d surface?

anonymous · Answer

Sure.  A box, a sphere, whatever so long as there's no opening in it.  An open surface has a hole in it.  So it could be like a window pane, or a disk, or a garbage bag that hasn't been sealed up.

anonymous · Answer

Gotcha- thanks!