[Getdp] basic permant magnet question - please help
Matt Koch
mattkoch at scitex.us
Sat Mar 17 03:39:56 CET 2007
Hello Pei-Ying,
seems to me that for this equation to be true, the magnetic field in a
permanent magnet would have to be constant in space. Outside of the
magnet it is H = nu*B and B = curl(A), so H = nu*curl(A), but inside the
magnet, it is H = Hc, i.e. the coercive field. There may be a
simplifying assumption here, like assuming that the magnetic field
inside a solenoid is constant in space.
Regards,
Matt Koch
Pei-Ying Hsieh wrote:
>
> Dear GetDP users:
>
> I just started learning about magnetism. I have a couple of basic
> questions that I am not able to figure out. It will be appreciated if
> someone here can shed some light on this.
>
> I have a permanent magnet - no electric current in the domain. I
> would like to calculate the magnetic flux density.
>
> I have found a 3D code posted by Jasper in 2006. The questions are:
>
> 1. The governing equation for magnetostatics filed is:
> Curl ( nu * Curl A) = J, where A is vector potential and J is
> electric current density.
> Now, since there is no current, I will think that J is zero.
> 2. In the Formulation of getdp code (2D Magnetostatics example on
> getdp wiki),
> it showed:
> Equation {
> Galerkin { [nu[] * Dof{ Curl a}, {Curl a}]; In
> Domain; Jacobian JVol; Integration I1; }
> Galerkin { [hc[], {Curl a}; In Domain_M; Jacobian
> JVol; Integration I1;}
> }
>
> How does {hc[], {Curl a}} come into the equation? I believe that hc is
> Coercitivity of the magnet?
>
> Thanks in advance for your reply!
>
> Best Regards,
>
> Pei
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