What is a magnetic circle?

All magnetism flows from north to south and a magnetic circle is the journey it takes to get from north to south.
Magnetism is usually generated by permanent magnets or electromagnets and passes through magnetic paths within the circuit. The circuit may also contain one or more "air gaps" filled with non-magnetic material. Magnetic circuits are used in devices such as motors, generators, and transformers as an efficient method of channeling magnetic fields.