[Getdp] basic permant magnet question - please help

[Pei-Ying Hsieh]

Thanks a lot Matt, Oliver, and Luigi for the detailed (but important to 
me) answer.

I get it now.

Best Regards,

Pei




Matt Koch <mattkoch at scitex.us> 
03/16/2007 10:39 PM
Please respond to
mattkoch at scitex.us


To
Pei-Ying Hsieh <pei-ying.hsieh at siemens.com>
cc
getdp at geuz.org
Subject
Re: [Getdp] basic permant magnet question - please help







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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