Magnetostatics. Calculate the magnetic flux density.

beyondlight

Problem description:

A wery long, than and flat metal plate of width 2a carries the total current I in the z-direction. The current density is uniformely distributed over the metal plate. A point P of particular interest is also shown in the figure, where the point has the position r=ax+ay.

Figure: http://tinypic.com/view.php?pic=4htkyt&s=5

Task: Calculate the magnetic flux density at point P.

Question:

I think the appropriate formula to calculate the flux density is

[itex]\int B \cdot dl= \mu I [/itex]

But the current is spread over the x-axis, so can i change the metal plate into a easier geometry that has the identical magnetic field, or an easier way to calculate the MFD, so to say?

beyondlight

Does this task maybe fit mor into the advanced forum?