Wrapping several turns of cable around a test object creates which type of magnetic field?

When several turns of cable are wrapped around a test object, it induces a magnetic field that primarily aligns along the length of the object, which is known as a longitudinal magnetic field. This occurs because the alternating current flowing through the wrapped cable generates a magnetic field that emanates from the coils and extends in a direction parallel to the axis of the test object.

In Magnetic Particle Inspection, a longitudinal magnetic field is often desirable as it can be used to detect surface and slightly subsurface defects that are oriented along the length of the test piece. The alignment of the magnetic field with the test object helps to ensure that any magnetic particles applied will be attracted to any discontinuities that might be present along the length of the specimen.

Understanding the nature of the magnetic field produced is crucial for properly performing inspections, as different fields may be more effective for detecting various types of flaws depending on their orientation and location relative to the magnetic field.