According to Gauss's law of magnetism, the total magnetic flux through a closed surface is zero. But during induction, we study that the magnetic field lines passing through a coil change, as does flux given by $\Phi = LI$. But even if they change, the net lines coming in= net lines going out. So, flux should be zero?
$\begingroup$
$\endgroup$
3
-
$\begingroup$ What do mean with: "net lines coming in= net lines going out"? $\endgroup$– Felix CrazzolaraCommented Jun 9, 2017 at 11:03
-
$\begingroup$ I mean that the total number of magnetic field lines are equal to the total number of magnetic field lines going out $\endgroup$– OFFplanetCommented Jun 9, 2017 at 11:05
-
1$\begingroup$ For coil magnetic flux, the surface the magnetic field lines pierce is not closed. $\endgroup$– Alfred CentauriCommented Jun 9, 2017 at 12:07
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
Gauss's law of magnetism does not give us a tool to "measure" flux. As you said it just says that the total magnetic flux through a closed surface is zero.
If we take a coil with changing magnetic field and imagine a sphere around it, Gauss law tell's us that the total flux through the surface of the sphere is zero, what helps us in no way.
Field lines are just a tool to represent intensity of the magnetic field with drawing (less) denser lines, and representing the direction the field at a given position. You can't argue with the "amount" of field lines.
But as you stated magnetic flux through a coil is given by $$\Phi = LI$$
So flux is not zero for $I, L \ne 0$.
$\begingroup$
$\endgroup$
According to Gauss' Law, the "net" magnetic flux is zero for a closed surface because magnetic monopoles don't exist but by writing $\Phi=LI$, we measure the outflux/influx produced by the single pole but though the "net" flux here also is zero.
