Answer: It completely expels magnetic field lines from its interior (Meissner effect), with susceptibility exactly -1.
- A It has mainly a small negative magnetic susceptibility like other ordinary diamagnets under usual circumstances
- B It completely expels magnetic field lines from its interior (Meissner effect), with susceptibility exactly -1
- C It is actually paramagnetic underneath, aligning weakly with the applied external field according to most researchers
- D It has exactly zero magnetic susceptibility, behaving magnetically just like a vacuum in the majority of cases studied
Correct answer: B. It completely expels magnetic field lines from its interior (Meissner effect), with susceptibility exactly -1
Explanation: Ordinary diamagnetism is weak (chi is about -10<sup>-5</sup>), but a superconductor exhibits perfect diamagnetism via the Meissner effect, completely expelling magnetic field lines with susceptibility exactly -1 - a qualitative jump, not just a stronger version of ordinary diamagnetism.
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.