Non-Destructive Testing (NDT) Practice Test

What defines the degree to which the primary magnetic field is weakened in eddy current testing?

1. The distance between the probe and the test piece

2. The amount of eddy currents present in the test piece

3. The temperature of the material being tested

4. The frequency of the testing device

The correct answer is: The amount of eddy currents present in the test piece

In eddy current testing, the degree to which the primary magnetic field is weakened primarily depends on the amount of eddy currents that are induced within the test piece. When an alternating magnetic field is applied through a probe, it penetrates the conductive material and generates eddy currents. The strength and distribution of these eddy currents are influenced by the material properties and the presence of flaws or inconsistencies within the test piece. When eddy currents flow, they create their own magnetic fields that oppose the original magnetic field due to Lenz's Law. This opposition leads to a reduction in the overall strength of the primary magnetic field. The more eddy currents that are produced, the greater the reduction in the primary field. Thus, accurately assessing the amount of eddy currents and understanding their impact is crucial for interpreting the results of eddy current testing effectively. Other factors, while they may influence the testing process, do not directly define the degree of weakening of the primary magnetic field in the same fundamental way that eddy currents do. The distance between the probe and the test piece can affect the strength of the magnetic field at that location, but it does not define the weakening itself. The temperature of the material can influence the conductivity and, consequently, the behavior