How can variations in particle size affect Magnetic Particle Testing?

Larger particles are indeed effective for detecting larger discontinuities, which makes this answer correct. The principle behind magnetic particle testing lies in the way magnetic particles are attracted to areas of flux leakage, which occurs around surface and near-surface discontinuities such as cracks and voids.

When larger magnetic particles are used, they can create a more pronounced magnetic concentration around larger defects due to their increased mass and visibility. This allows inspectors to more easily identify these discontinuities during examination. Larger particles tend to accumulate at defect sites more effectively, resulting in clearer and more noticeable indications that are easier to interpret.

In contrast, smaller particles could be more apt for detecting finer defects since they can penetrate more easily into smaller surface openings or cracks. However, they may not present as strong a signal or indication for larger discontinuities.

The idea that particle size has no relation to defect detection is incorrect because the effectiveness of the testing method can vary significantly based on the size of the magnetic particles used in relation to the size of the defects being inspected.