Q.'The net magnetic flux through any closed surface is zero'. This law is called

Gauss' law of magnetism states that the net magnetic flux through ANY closed (Gaussian) surface is always exactly zero: $\oint\vec B\cdot d\vec A=0$. This is the direct magnetic analogue of Gauss' law of electrostatics, $\oint\vec E\cdot d\vec A=q_{enclosed}/\varepsilon_0$, but with one crucial difference: the electric law's right-hand side depends on the enclosed electric charge, while the magnetic law's right-hand side is identically zero for every possible closed surface, because there is no such thing as enclosed "magnetic charge" -- isolated magnetic poles do not exist.

This can be seen concretely by comparing a bar magnet (or a current-carrying solenoid, which produces an identical external field pattern) with an electric dipole. A Gaussian surface that does not enclose either pole trivially has equal numbers of field lines entering and leaving. A surface that DOES enclose just the north pole of the magnet might seem, at first, to have more lines leaving than entering -- but any physically realisable thin slice of a magnet still contains both a north-type and a south-type region (since poles are never isolated), so the enclosed net "magnetic charge" remains zero and the flux still comes out to zero. This is fundamentally different from the electric-dipole case, where a surface enclosing just the positive charge DOES have a gen …