In magnetic particle testing, which option describes the current used to detect subsurface defects?

In magnetic particle testing, which option describes the current used to detect subsurface defects?

• A. It uses alternating current (AC)
• B. It uses no electrical current
• C. It uses direct current (DC)
• D. It uses pulsating current

Answer: (C)

In magnetic particle testing, how the part is magnetized determines how deeply the field penetrates the material. A steady direct current produces a constant magnetic field that penetrates deeper, so leakage fields from subsurface flaws can reach the surface and be visualized with the magnetic particles. Alternating current changes polarity rapidly and tends to affect the flux near the surface, making it more effective for surface-breaking defects. If no current flows, there’s no magnetization to create leakage fields at defects. Pulsating current isn’t the standard description for detecting subsurface flaws.

In magnetic particle testing, how the part is magnetized determines how deeply the field penetrates the material. A steady direct current produces a constant magnetic field that penetrates deeper, so leakage fields from subsurface flaws can reach the surface and be visualized with the magnetic particles. Alternating current changes polarity rapidly and tends to affect the flux near the surface, making it more effective for surface-breaking defects. If no current flows, there’s no magnetization to create leakage fields at defects. Pulsating current isn’t the standard description for detecting subsurface flaws.