Effect of magnetic field on superconductivity When a material is in the superconducting state and an external magnetic field is applied, what is the correct outcome regarding its superconducting property?

Introduction / Context:
Superconductors exhibit zero DC resistance and the Meissner effect (expulsion of magnetic flux). However, these properties hold only below certain critical parameters: temperature, magnetic field, and current density. Recognizing the critical field concept is essential for magnet design, power devices, and cryogenic systems.

Given Data / Assumptions:

• Material is superconducting initially (T below critical temperature Tc).
• A magnetic field is applied externally.
• Critical field Hc (or Hc1, Hc2 for type-II) limits exist.

Concept / Approach:

For type-I superconductors, superconductivity is destroyed when the applied field exceeds the thermodynamic critical field Hc. For type-II superconductors, superconductivity persists in a mixed state between Hc1 and Hc2, but is destroyed above Hc2. Hence, in general, an applied field can terminate superconductivity if it is strong enough, making option (c) correct.

Step-by-Step Solution:

Verification / Alternative check:

Experimental magnetization curves show flux expulsion and sudden loss of superconductivity beyond critical fields; practical superconducting magnets operate well below Hc2 to avoid quenching.

Why Other Options Are Wrong:

(a) ignores critical fields; (b) introduces a “small resistivity” concept inconsistent with the definition; (d) insulator behavior is unrelated; (e) superconductors are not paramagnets in the Meissner state.

Common Pitfalls:

Confusing type-II mixed states with finite resistance (they still carry DC without loss below Jc), and ignoring the role of pinning and quench behavior.

Final Answer:

The superconducting property may be destroyed (above a critical field)