Solid State Physics-II

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Chapter#5: Introduction to Super Conductor

Team Quanta gladly presents all possible short questions of BS Physics book Solid State Physics – II’s Chapter#5: Introduction to Super Conductor.

Q.5.1:- What is superconductivity?

Superconductivity is defined as the phenomenon in which the electric resistance of a substance drops suddenly drops to zero when it is cooled below a certain temperature. There are at least 25 super conducting elements and much larger numbers of superconducting alloys.

Q.5.2:- Superconductor are perfectly diamagnetic in nature. Why?

Superconductor are perfectly diamagnetic in nature because when the temperature is raised from below critical temperature then magnetic flux suddenly penetrates the specimen. Since the magnetic induction in a superconductor is a perfect diamagnetic in nature.

Q.5.3:- What is Meissner effect?

Expulsion of magnetic lines of force from a susceptibility material when it is cooled below transition temperature in a magnetic field is called Meissner effect.

Q.5.4:- What is cooper pair?

The net effect is the attraction of two electrons via a lattice distortion or phonon to form a pair of electron known as the cooper pair. Cooper calculated the size of copper pair as;

    \[r_o=\frac{\hbarV_F}{E_B}\]

V_F is the velocity of electrons in a metal.

Q.5.5:- What is the critical magnetic field of superconductor.

The minimum applied magnetic field necessary to destroy superconductivity and restore the normal resistivity is called critical magnetic field.

Q.5.6:- Give any three main characteristics of superconductor.

  • The electrical properties of material get totally changed.
  • All thermoelectric effects ( Seebeck, Peltier, Thomson) disappear in superconductivity.
  • The specific heat changes discontinuity at the transition temperature.

Q.5.7:- What is magnetic susceptibility of a superconductor?

    \[B=\mu_o(H+I)\]

For a superconductor B= 0

    \[\mu_o \left(H+I\right)=0\]

∵\mu_o \neq0

    \[H+I=0\]

∵ I=-H

Magnetic susceptibility \chi_m is defined as;

    \[\chi_m=\frac{I}{H}\]

    \[\chi_m=-\frac{H}{H}\]

    \[\chi_m=-1\]

The magnetic susceptibility for a superconductor is equal to -1.

Q.5.8:- Differentiate between type-I and type-II superconductor.

Type-I: Type-I superconductor are also known as soft superconductor. They are perfectly diamagnetic. They follow Meissner effect. They completely expel the magnetic field.

Type-II: Type-II superconductor are also known as hard superconductor. They do not follow meissner effect strictly. They also expel the magnetic field.

Q.5.9:- Explain the result when x=λ and x>>λ in the following equation B=B°e-x/⋋.

For x= λ                  

B=B°e-x/⋋

B=B°e–⋋/⋋  

B=B°e–1 

B=B°1/e       

Q.5.10:- Define penetration depth for a superconductor. What is its value for critical temperature?

The measure of the distance from the surface of the superconductor at which the magnetic field of lines decays to  of  its value at the surface of superconductor.

    \[\leftthreetimes_o=\sqrt{\frac{m}{\mu_o n_se^2}}\]

⋋ contain ns which varies with temperature.

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