Discontinuities are most easily detected when eddy currents are:

Eddy currents are induced in the material being tested when an alternating magnetic field is applied. The effectiveness of detecting discontinuities—such as cracks or voids—depends heavily on the orientation of these eddy currents in relation to the discontinuity.

When eddy currents are perpendicular to the major plane of the discontinuity, they create a stronger disruption in the flow of current as they encounter the discontinuity. This disruption is more pronounced because the eddy currents will change direction and intensity as they encounter a boundary where the material properties change, such as at a crack or void. This results in a more significant signal that can be detected by the testing equipment.

In contrast, when the eddy currents are coplanar or parallel to the discontinuity, the disruption is less pronounced. The currents may flow past the discontinuity without significantly altering their path or creating a detectable signal, making it more difficult to identify the existence of such flaws.

Understanding the angle at which eddy currents interact with discontinuities is critical for enhancing the sensitivity and effectiveness of the Eddy Current Testing technique.