# Plot Magnetic field normal component along a line over a surface

Dear all,

I kindly ask if is possible, with the aid of the Fields Calculator, define a Named Expressions able to plot the normal component of the magnetic field over a surface (this will generate a scalar value on a surface SclSrf) and then evaluate these scalar value only alog a definited circular path that is on this surface.

I think about this approach in order to use it to evaluate the normal component of the field along a circular curve that is parallel to the XY global plane at a fixed z coordinate. The tangential components over a circular path is easy to evaluate by using the Tangent, but for the Normal it require a surface so may be an approach (if is possible) calculate the normal scalar value over a surface that intersect the curve and then extract only the values on this curve, may be a possible/valid approach? There are other approach?

Thank!

## Answers

Hi, @FIREFOX ,

You first can define a named expression in field calculator to calculated surface normal by selecting the field vector, selecting UnitVec-->normal, and creating Scl : Dot(<Bx,By,Bz>, SurfaceNormal). You can use this named expression to plot magnitude of surface normal of that field on any surface.

To plot normal vector on a line/path, a method could be to draw a very thin surface of large aspect ratio to approximate the curved path/line. Then plot the defined named expression on that thin surface.