Answer: The two poles experience equal and opposite forces that form a couple unless the magnet is aligned with the field.
- A The north pole of the magnet interacts with the field, while the south pole stays unaffected in most observed cases
- B The magnet's poles experience forces mainly when the field is non-uniform, rather than when it is uniform under typical physiological conditions
- C The two poles experience equal and opposite forces that form a couple unless the magnet is aligned with the field
- D A uniform field exerts force on a magnet but produces no torque on it according to standard texts in general clinical practice
Correct answer: C. The two poles experience equal and opposite forces that form a couple unless the magnet is aligned with the field
Explanation: In a uniform field, the equal and opposite forces on the two poles cancel to give zero net force but, unless the dipole is aligned with the field, they act at different points and create a net torque.
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.