Flux distribution in a permeable sheet with a hole near an edge

In the measurement of the distribution of magnetic flux in the cores of electrical machines by locating search coils in them, the presence of a search-coil will alter the flux in that region. It is therefore necessary to make a correction to the measured flux. The problem is the solution of Laplace´s equation in two dimensions in a material assumed to be of constant permeability, and it has an analogy in hydrodynamics. The solution is obtained by a conformal transformation; it is found that the correction is quite significant when the distance of the centre of the hole from the edge is equal to its diameter.