Nondestructive Eddy Current Testing

When a coil is placed in proximity to a conductor, the magnetic field in the vicinity of the coil is altered by eddy currents in the conductor. The conductivity of a sample material may be determined by measuring the field. Closed-form solutions are presented for the magnetic field at the surface of a semi-infinite conductor for two cases: a semi-infinite coil, the end of which is in contact with the conductor, and a loop of wire on the surface of the conductor.