Definition
A magnetic field that flows in a circular path around and through a part, produced by passing electric current through the part itself. It is used in magnetic particle inspection to reveal cracks or flaws that run lengthwise (parallel to the long axis) of the part.
Plain English
When you push electricity through a metal part, a ring-shaped magnetic field forms around it. That field makes lengthwise cracks show up when iron powder is applied, because the powder gathers at the breaks in the field.
Context Anchor
Seen in aircraft maintenance and engine-part inspection, especially when using magnetic-particle methods to check metal parts for cracks.
Derivation
From Latin circulus, meaning a small ring or circle. The term simply describes the shape of the magnetic field — it loops around the part in circles, rather than running end to end.
Why Pilots Care
Technicians must account for it when routing wires near compasses to prevent unwanted magnetic interference.
Grounding Statement
Picture electricity flowing through a metal shaft while the magnetic field wraps around that shaft in invisible circles.
Intuition Check
Circular does not mean the aircraft part has to be round. Here, circular describes the direction of the magnetic field as it wraps around the current path.
Example Sentence 1
The technician used circular magnetism to inspect the crankshaft for lengthwise cracks before reinstalling it.
Example Sentence 2
Higher current through the conductor produces stronger circular magnetism around it.