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 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.