Answer: 2m/.
- A 2m/π
- B m/π
- C m/2
- D πm/2
Correct answer: A. 2m/π
Explanation: If length L = πr, bending gives pole separation equal to the diameter 2r = 2L/π. New moment = pole strength × 2r = m × (2/π) = 2m/π.
Magnetic field of a bar magnet: field lines emerge from the north pole and re-enter at the south pole outside the magnet, forming continuous closed loops. Image: Geek3, CC BY-SA 3.0, via Wikimedia Commons.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.