View source for Gauss's Law (Magnetic):

= Gauss's Law (Magnetic): Definition and Mathematical Representation =

== Introduction ==
'''Gauss’s Law for Magnetism''' is one of the four fundamental [[Maxwell's Equations]] in electromagnetism. It states that the total magnetic flux through any closed surface is zero, implying that magnetic monopoles do not exist (i.e., every magnetic field line that enters a surface also exits it).

== Mathematical Formulation ==

=== Integral Form ===
<math>
\oint_{\text{closed surface}} \vec{B} \cdot d\vec{A} = 0
</math>

Where:
* <math>\vec{B}</math> is the magnetic field vector (in tesla, T),
* <math>d\vec{A}</math> is a vector representing an infinitesimal area on the closed surface, pointing outward.

This means that the net magnetic flux through any closed surface is always zero.

=== Differential Form ===
By applying the divergence theorem to the integral form, we obtain the differential form:

<math>
\nabla \cdot \vec{B} = 0
</math>

This states that the divergence of the magnetic field is zero everywhere.

== Physical Meaning ==
Gauss's Law for Magnetism implies:
* There are no isolated magnetic charges (magnetic monopoles).
* Magnetic field lines are continuous loops — they do not begin or end, but form closed curves.
* The number of field lines entering a closed surface equals the number leaving it.

== Visualization ==
* For a magnetic dipole (e.g., a bar magnet), field lines emerge from the north pole and enter the south pole, but ultimately form closed loops.
* No matter the Gaussian surface used, the total magnetic flux will always be zero.

== Comparison with Gauss’s Law (Electric) ==
{| class="wikitable"
! Gauss’s Law (Electric) !! Gauss’s Law (Magnetic)
|-
| <math>\nabla \cdot \vec{E} = \frac{\rho}{\varepsilon_0}</math> || <math>\nabla \cdot \vec{B} = 0</math>
|-
| Describes field due to electric charges || Implies no magnetic monopoles
|-
| Electric field lines start and end on charges || Magnetic field lines form closed loops
|}

== Implications ==
* No magnetic monopoles have been observed in nature.
* Magnetic dipoles (e.g., bar magnets, current loops) are the fundamental sources of magnetic fields.
* Magnetic fields must always form closed-loop configurations.

== Applications ==
* Used in verifying and constructing magnetic field models in symmetry-based systems.
* Essential in [[Magnetostatics]], [[Electromagnetic Induction]], and [[Electromagnetic Wave]] theory.
* Important in the design of devices like magnetic shielding, inductors, and transformers.

== See Also ==
* [[Maxwell's Equations]]
* [[Gauss's Law (Electric)]]
* [[Magnetic Field]]
* [[Magnetic Flux]]
* [[Magnetic Dipole]]
* [[Electromagnetism]]
* [[Faraday's Law]]