# Changes

## Ampere's law

505 bytes added, 03:14, 24 September 2008
'''Ampere's Law''' , named for [[Andre-Marie Ampere]], relates electric [[current]] to [[magnetic field]]s, and is a law that simplifies one of [[Maxwell's Equations]]. It is often used in the calculation of the [[magnetic field]] at a point due to one or many [[current]]-carrying wires. It has many similarities is the magnetic analogue to [[Gauss's Law]], and can be stated in integral form as:
: $\oint_S oint_C \vec{B} \cdot \mathrm{d}\vec{s} = \mu_0 I_{\mathrm{enc}}$
where $\vec{B}$ is magnetic field, ''C'' is a closed curve, $I_{\mathrm{enc}}$ is current enclosed by ''C'', and $\mu_0$ is the permeability of free space.

In differential form, Ampere's Law is written

:$\vec{\nabla}\times\vec{B}=\mu_0\vec{J}$

where $\vec{J}$ is current density.

[[category:Physics]]
[[category:Electricity]]
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