ET ASNT Level II Practice Exam

Eddy current testing is fundamentally based on the principle of electromagnetic induction. This principle describes how a conductor, when exposed to a changing magnetic field, induces a flow of electric current within the material. In eddy current testing, an alternating current is passed through a coil, creating a magnetic field. When this field interacts with a conductive material, it induces circular currents (eddies) in that material.

These eddy currents produce their own magnetic fields, which can affect the original magnetic field of the coil. The response of the eddy currents, including their strength and phase, can provide valuable information about the electrical and material properties of the conductor being tested, such as its conductivity, thickness, and the presence of flaws or defects.

The other principles listed do not accurately describe the mechanism behind eddy current testing. Magnetostriction relates to the change in length of a material when subjected to a magnetic field, piezoelectric energy conversion involves the generation of electric charge in certain materials when stressed, and magnetomotive force pertains to the magnetization process within magnetic materials. None of these principles encompass the core concept of inducing currents through changing magnetic fields, which is essential to the functioning of eddy current testing.