# [Getdp] vector normal to a magnet

Patrick Dular Patrick.Dular at ulg.ac.be
Tue Oct 15 08:50:49 CEST 2013

```Joseph,

Because Atan2[Y[],X[]]] gives you the angle made by the position vector
( X[] , Y [] ) (of each current point in the XY-plane, i.e. each point
where this function has to be evaluated) (see
http://en.wikipedia.org/wiki/Atan2), the Vector[] function

Vector[ Cos[Atan2[Y[],X[]]], Sin[Atan2[Y[],X[]]], 0 ]

gives a radial vector at this point (which can be checked on your field
map: the direction of the field in the magnets is mainly the radial one.

Cos[Atan2[Y[],X[]]] is the X-projection of the unit radial vector.
Sin[Atan2[Y[],X[]]] is the Y-projection of the unit radial vector.

To define the direction you wish for the remanent induction in each
magnet, you should use the function I sent you yesterday. If you wish,
send me your .geo and .pro files and I will implement it for you.

Patrick

On 14/10/13 20:42, Joseph Frippiat wrote:
> I don't understand the Vector[] usage..
>
> With this :
>
>   For k In {1:nbMagnets}
>     br[ Rotor_Magnet~{k} ] = b_remanent * Vector[ Cos[Atan2[Y[],X[]]],
> Sin[Atan2[Y[],X[]]], 0 ];
>   EndFor
>
> I have a b field (not the wanted one) :
>
>
>
> With this :
>
>   For k In {1:nbMagnets}
>     br[ Rotor_Magnet~{k} ] = b_remanent * Vector[
> Cos[Atan2[Y[],X[]]+Pi/4], Sin[Atan2[Y[],X[]]+Pi/4], 0 ];
>   EndFor
>
> I have nothing :
>
>
>
> Why ?
>
> Joseph
>
> --
>
> Joseph Frippiat
> Senior Developer - UPS Division
>
> *KST S.A.* - Site of Battice
> Cour Lemaire, 16
> B-4651 BATTICE
> BELGIUM
> Tel : +.32.4.247.01.67
> Fax : +.32.87.31.42.21
> E-mail : frippiat.j at kst.be
> Web : www.kst-ups.com
>
> Head office : Cour Lemaire, 16 - 4651 Battice (Belgium)
> RPM Liège (Belgium) : 0423.472.603
>
>
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```