Eddy current inspection is one of several NDT methods that use
the principal of electromagnetism as the basis for
conducting examinations. Several other methods such as Remote
Field Testing (RFT), Flux Leakage and Barkhausen Noise also use
Eddy currents are created through a process called electromagnetic
induction. When alternating current is applied to the conductor,
such as copper wire, a magnetic field develops in and around the
conductor. This magnetic field expands as the alternating current
rises to maximum and collapses as the current is reduced to zero.
If another electrical conductor is brought into the close proximity
to this changing magnetic field, current will be induced in this
second conductor. Eddy currents are induced electrical currents
that flow in a circular path. They get their name from eddies
that are formed when a liquid or gas flows in a circular path
around obstacles when conditions are right.