Non-Destructive Testing (NDT) Practice Test

What is a characteristic of ferromagnetic materials?

1. They are weakly magnetic

2. They have a high positive susceptibility to external magnetic fields

3. They cannot be magnetized

4. They are primarily non-metallic

The correct answer is: They have a high positive susceptibility to external magnetic fields

Ferromagnetic materials are characterized by their high positive susceptibility to external magnetic fields. This means they can easily become magnetized in the presence of a magnetic field and retain that magnetization even after the external field is removed. This property is due to the alignment of magnetic domains within the material, which can enhance the overall magnetic effect. In contrast, materials that are weakly magnetic do not have the same level of responsiveness to external magnetic fields, hence are not classified as ferromagnetic. Similarly, the statement that ferromagnetic materials cannot be magnetized is fundamentally incorrect, as their ability to be magnetized is one of their defining features. Additionally, the notion that ferromagnetic materials are primarily non-metallic does not hold, as the most common examples of ferromagnetic materials, such as iron, nickel, and cobalt, are indeed metals. These distinctions are what solidify the significance of high positive susceptibility in defining ferromagnetic materials.