Directions: Each of the next items consists of two statements, one labeled as the `Assertion (A)' and the other as 'Reason (R)' You are to examine these two statements carefully and select the answers to these items using the codes given below :

Assertion (A): Good conductors do not show superconductivity.

Reason (R): Electron-phonon interaction. that leads to the formation of Cooper pairs is weak in good conductors. 
 

Concept:

Assertion

Good conductors are capable of transporting about an ampere of current through them with a small amount of resistance.

Examples would be copper(Cu), gold(Au), etc.

Superconductors are those materials that are usually bad conductors at room temperature but when the temperature is decreased to very low, the resistance becomes zero.

Examples might be : mercury(Hg), silicon(Si), Germanium(Ge) etc.

Good conductors can't be transformed into superconductors.

The assertion is true.

Reason 

It is the electron-phonon interaction that laid the foundation for the theory of superconductivity in the form of Cooper pairs in conventional superconductivity (BCS theory)

Cooper showed that the random small attraction between the electrons in a metal can cause a paired state of electrons to have a lower energy level than the Fermi energy level, which implies that the pair is bound.

• Among most of the chemical elements, cooper pairing is accomplished through vibrations at the molecular level within the crystal lattice.
• Atoms in FCC cell are packed so tightly that lattice vibrations essential for cooper pairing are constrained.
• Copper, Silver, and Gold have a tightly packed lattice structure called Face Centred Cubic unit cell as shown above.

Reason is true

Conclusion:

Since the superconductivity depends on the electron-phonon interaction it is the true and correct explanation for Statement I

Both A and R are individually true and R is the correct explanation of A.