Superconductors are defined as perfect conductors under what condition?

Superconductors are defined as perfect conductors under what condition?

• A. They become perfect conductors only below a very low temperature.
• B. They conduct electricity with infinite resistance.
• C. They remain perfect conductors at any temperature.
• D. They require strong magnetic fields to conduct.

Answer: (A)

Zero resistance occurs only when the material is cooled below its critical temperature. Below this temperature, electrons pair up into Cooper pairs and move without scattering, so current can flow without energy loss. Above the critical temperature, the material behaves like a normal conductor with finite resistance. Magnetic fields also play a role: strong fields can destroy superconductivity, so the zero-resistance state is not maintained there. So the defining condition is being below the critical temperature, which makes the material a perfect conductor in that phase.

Zero resistance occurs only when the material is cooled below its critical temperature. Below this temperature, electrons pair up into Cooper pairs and move without scattering, so current can flow without energy loss. Above the critical temperature, the material behaves like a normal conductor with finite resistance. Magnetic fields also play a role: strong fields can destroy superconductivity, so the zero-resistance state is not maintained there. So the defining condition is being below the critical temperature, which makes the material a perfect conductor in that phase.