Non-Destructive Testing (NDT) Practice Test

How can ferromagnetic materials become magnetized?

1. By heating them to critical temperatures

2. By aligning the magnetic domains within the material

3. By exposing them to permanent magnets

4. By increasing their size

The correct answer is: By aligning the magnetic domains within the material

Ferromagnetic materials become magnetized primarily through the alignment of their magnetic domains. These materials consist of numerous tiny regions called magnetic domains, each possessing a magnetic moment. In an unmagnetized state, these domains are oriented randomly, which cancels out their magnetic effects. When a ferromagnetic material is exposed to an external magnetic field, the magnetic moments within these domains begin to align in the direction of the field. As a larger number of domains become aligned, the overall magnetization of the material increases. This alignment can be achieved through various means, such as applying a strong external magnetic field or through a process known as magnetization. The degree of magnetization depends on factors such as the strength of the external magnetic field and the intrinsic properties of the material. Thus, the method of aligning the magnetic domains is fundamental to the process of magnetization in ferromagnetic materials.