Non-Destructive Testing (NDT) Practice Test

A key feature of eddy current probes is that they are designed to interact with what type of surface?

1. Non-conductive surfaces

2. Conductive surfaces

3. Magnetic materials

4. Insulated wires

The correct answer is: Conductive surfaces

Eddy current probes are specifically designed to interact with conductive surfaces. This is because eddy current testing is based on the principle of electromagnetic induction, where an alternating current is passed through a coil, generating a changing magnetic field. When this probe is brought near a conductive material, eddy currents are induced within the material, which can then be measured. The characteristics of these eddy currents, such as their amplitude and phase shift, can provide valuable information regarding the conductivity, thickness, and any defects present in the conductive material being inspected. The effectiveness of eddy current testing is dependent on the conductivity of the material being tested; thus, materials that do not conduct electricity, such as non-conductive surfaces, cannot generate eddy currents, making them unsuitable for this type of inspection. Similarly, while magnetic materials are conductive and can be tested using eddy current probes, the focus is primarily on the interaction with conductive surfaces in general. Insulated wires may involve conductive elements but are also not the primary focus since the insulation would prevent direct interaction with the conductive material itself.