Magnetic Particle Inspection Level 1 Practice Exam

What is a simple method of demagnetizing a test object?

1. Direct current

2. Alternating current

3. Heat treatment

4. Mechanical shock

The correct answer is: Alternating current

When demagnetizing a test object, the use of alternating current (AC) is a fundamental method. This process involves subjecting the magnetized material to an alternating magnetic field, which gradually reduces the intensity of the magnetic field within the object. As the alternating current is applied, the magnetic domains within the material realign in various directions due to the shifting polarity of the AC. This realignment disrupts the uniform orientation of the magnetic domains that causes the magnetization, effectively demagnetizing the object. In contrast, direct current (DC) tends to enhance or maintain the existing magnetization rather than demagnetize it. Heat treatment can assist in demagnetizing materials with specific magnetic properties but may not always be effective for all types of materials and could potentially alter the physical properties of the test object. Mechanical shock can also demagnetize objects by disrupting the alignment of magnetic domains; however, it is less controlled and reliable compared to using alternating current. Thus, alternating current stands out as a simple and effective method for demagnetizing a test object in the context of magnetic particle inspection.