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An EMAT is an Electro-Magnetic Acoustic Transducer which couples to a metalic sample through electromagnetic forces.
Thus the EMAT need not touch the metal sample. The EMAT is a non-contact device. The elecromagnetic coupling works
on two different principals. Non-ferromagnetic materials use a Lorentz force mechanism where a curent in a magnetic
field creates a force. In ferro magnetic materials the metal changes shape in the presence of a magnetic field. Placing a
current carrying conductor in the magnetic field near the metal surface chnages the field as a function of the wire current
and thus effects the shape of the adjacent metal. This is know as magnetostrictive coupling and can be much larger than
Lorentz forces as the material is displaced directly as oppossed to forces being applied. See Fig.1 for an illustration of a
typical EMAT configuration.

FIGURE 1: Basic EMAT Configurations: a tangential magnetic field makes forces normal to the surface and a
normal field makes tangential, shearing forces.