What does an eddy current test primarily detect?

An eddy current test primarily detects the surface condition of conductive materials. This non-destructive testing method utilizes electromagnetic induction to produce eddy currents in conductive materials when exposed to an alternating magnetic field. These eddy currents flow near the surface of the material, and their behavior is influenced by various factors such as the electrical conductivity, magnetic permeability, and the presence of defects like cracks or corrosion near the surface.

By analyzing the characteristics of the eddy currents, such as their amplitude and phase shift, inspectors can determine the surface conditions and identify any flaws that might compromise the integrity of the material. This makes it particularly effective for assessing the surface condition and detecting surface-breaking defects in metals.

In comparison, the other options do not accurately reflect the main capabilities of eddy current testing. While it does provide some insights about internal defects due to variations in conductivity, it is not primarily designed for that purpose. Similarly, temperature measurement and tensile strength assessment are outside the scope of what eddy current testing directly evaluates. Thus, option B correctly identifies the primary function of the eddy current test in assessing the surface condition of conductive materials.