Answer: m/2.
- A m/4
- B m/2
- C m
- D 2m
Correct answer: B. m/2
Explanation: Cutting perpendicular to the axis halves the length (and pole strength stays), so each moment is m/2.
Magnetic field lines form closed loops: outside the bar magnet they run from the N pole to the S pole; inside, they continue from S back to N, so the lines never start or end anywhere.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.