When does a normal conductor become a superconductor?
The temperature at which a normal conductor loses its resistivity and becomes a super conductor is knows as transition temperature or critical temperature.
In which of the following does the residual resistivity exist?
When the temperature is reduced to 0K, the resistivity of the impure metal doesn’t become zero, because there exist some impurities which gives rise to minimum resistivity known as residual resistivity.
Meissner effect occurs in superconductors due to which of the following properties?
A diamagnetic material has a tendency to expel magnetic lines of forces. Since the super conductor also expels magnetic lines of force it behaves as a perfect diamagnet. This behaviour is first observed by Meissner and is hence called Meissner effect.
What happens when a large value a.c. current is passed through super conductors?
When a large value of a.c. current is applied to a super conducting material it induces some magnetic field in the material and because of this magnetic field, the superconducting property of the material is destroyed.
How is persistent current produced in supermagnets?
When dc current of large magnitude is once induced in a super conducting ring then the current persists in the ring even after the removal of the field. This current is called persistent current. This is due to diamagnetic property. The magnetic flux inside the ring will be trapped in it and hence current persists.
Superconductors can be used as a memory or storage elements in computers. True or false?
Since the current in superconducting ring can flow without any change in its value, it can be used as a memory or storage element in computers.
Superconducting tin has a critical temperature of 3.7K at zero magnetic field and a critical field at 0.0306 Tesla at 0K. Find the critical field at 2K.
Critical field, Hc = H0 [1-T2/(Tc)2 )] Critical college = 0.02166 Tesla
Calculate the critical current for a wire of lead having a diameter of 1mm at 4.2 K. Calculate temperature for lead is 7.18 K and Hc = 6.5×104 A/m. Critical field is 42.758×103 A/m.
Critical current Ic = 2πrHc
Ic = 134.26 A