Answer: mB.
- A mB
- B 2mB
- C mB/2
- D Zero
Correct answer: A. mB
Explanation: W = mB(cosθ<sub>1</sub> - cosθ<sub>2</sub>) = mB(cos0 - cos90) = mB(1 - 0) = mB.
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.