Final answer:
Alternating current (AC) is used for detecting surface defects, while direct current (DC) is typically utilized for identifying subsurface defects during magnetic particle inspection.
Step-by-step explanation:
When performing a magnetic particle test to detect subsurface defects, alternating current (AC) or direct current (DC) can be used. The choice between AC and DC depends on the depth of the defects that need to be detected. For surface defects, AC is often preferred because it provides good defect detection on or near the surface due to its skin effect. However, for detecting subsurface defects, DC is typically used because it penetrates deeper into the material, thereby providing better detection capabilities for flaws that are not immediately at the surface.
The type of current used to detect subsurface defects when using a magnetic particle test is alternating current (AC).In a magnetic particle test, an AC current is passed through the material being inspected, creating a magnetic field. If there are any subsurface defects, such as cracks or voids, the magnetic field will be disrupted and reveal the presence of the defect. This technique is commonly used in non-destructive testing of metal components for quality control and safety purposes.