When checking an item with the magnetic particle inspection method, circular and longitudinal magnetization should be used to:

To reverse all types of defects.

Explanation:

In the magnetic particle inspection method the material which is used in testing will utilize the magnet which is ferromagnetic and it is high permeable and the retentivity of this magnet is low.

It is a technique which is not destructive and this technique is used for detecting the surface and the hollow part of ferromagnetic substance and will reverse all these defects.

Therefore, circular and longitudinal way of magnetization will reverse all the types of defect.