SUPERCONDUCTIVITY MEISSENER EFFECT TYPES OF SUPER CONDUCTORS

1. BELL 301 MATERIAL
SCIENCE
BY PRASHANT KUMAR
ASST. PROFESSOR
MITS GWALIOR

2. MEISSENER’S EFFECT
When the superconducting material is subjected to a
uniform magnetic field, under the condition T <Tc
and H< Hc, the magnetic flux lines are excluded
from the material. Thus the material exhibits perfect
diamagnetism. This phenomenon is called as
Meissner effect.

3. MEISSENER’S EFFECT
CONTINUED…..

4. PROPERTIES OF SUPERCONDUTORS
1. Zero Electrical Resistance : The electrical resistivity drops to zero at the transition temperature.( Tc)
2. Effect of magnetic field (Bc) : Below temp Tc, the superconducting property disappears when strong
magnetic field is applied. i.e., it returns to normal state.
3. Diamagnetic property : The superconductor is a perfect diamagnetic.
4. Effect of heavy Current : The superconducting property disappears when a heavy current flows, since
current flow will set up a magnetic field. ( Large electric current – induces magnetic field – destroys
superconductivity • Induced Critical Current Ic = 2πrHc)
5. Isotope effect : The presence of isotopes in superconductors changes the transition temperature of the
superconductors.
6. Thermal properties : Entropy and specific heat decreases at transition temperature and the
thermoelectric effect disappear in the superconducting state.
7. Effect of Impurities : The impurities change the magnetic properties of the superconductors.
0
1
r
m



 

5. CRITICAL TEMPERATURE
The transition temperature (Tc) is the critical temperature below
which the resistivity of the material suddenly changes to zero.

6. CRITICAL MAGNETIC FIELD
When the superconducting materials are subjected to a strong
magnetic field, it will result in the destruction of the superconducting
property. i.e, they return to the normal state. The minimum field
required to destroy the superconducting property is called the critical
field (Hc). The variation of Hc with temperature is as shown.
H0 – Critical field at 0K
T - Temperature below TC
TC – Transition Temperature2
0 1C
C
T
H H
T
  
   
   

7. CRITICAL CURRENT DENSITY
Critical current density (Jc)
The application of a large value of electric current to a
superconducting material destroys its superconducting property. The
current required for this is called critical current (Ic) and
corresponding current density is called critical current density (Jc)

8. TYPE I & TYPE II SUPER
CONDUCTORS
Type I superconductors
the superconductivity disappears
as T > Tc | B > Bc | J > Jc
Type II superconductors
For Bc1 < B < Bc2 there is a
partial flux penetration
called mixed phase

9. TYPE I AND II

10. MIXED BEHAVIOUR IN TYPE II

11. TYPE I AND TYPE II

12. TYPE I TYPE II

13. APPLICATION OF
SUPERCONDUCTOR
For the production of high magnetic fields.
In high energy physics experiments.
In NMR imaging.
In magnetohydrodynamic power generation.
In magnetic separation for refining ores and chemicals.
As memory storage element in computers.
In superconducting generators and motors.
In superconducting fuses, switches and cables.
In Superconducting Quantum Interference Device (SQUID).
In levitating trains.

15. TRANSISTOR
CLASSIFICATION
BJT
• Npn type
• pnp type)
FET (Field effect
transistors)
• N channel FET
• P channel FET
MOSFET
(metal oxide
field effect
transistors)
• NMOS
• PMOS