What is the principle underlying Eddy Current Testing (ET)?

Eddy Current Testing (ET) is based on the principle of electromagnetic induction. This principle refers to the generation of electrical currents within a conductor when it is subjected to a changing magnetic field. In the context of ET, a probe with alternating current generates a magnetic field, which induces eddy currents in the conductive material being tested.

These induced currents flow in loops within the material and their behavior is affected by the material's properties, such as conductivity, permeability, and the presence of any defects. By analyzing the resulting magnetic field and the changes in the characteristics of the induced eddy currents, technicians can detect various types of discontinuities and assess the integrity of the material being inspected.

The other options do not reflect the core operating principle of ET. For instance, thermal conductivity measurement relates to temperature gradients and their effects on material properties, while ultrasonic wave reflection involves sound waves rather than electromagnetic principles. X-ray fluoroscopy is a radiographic technique that examines the internal structure of materials using X-rays, which is entirely different from the electromagnetic mechanisms employed in Eddy Current Testing.