CHAPTER THREE
SUPERCONDUCTIVITY
Outlines
3.1 Theory of superconductivity
3.2 Meissner effect
3.3 Classification of superconductor materials
3.4 London equation
3.5 Application of superconductor
Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, as
he studied the properties of metals at low temperatures.
n his laboratory the DC resistivity of mercury suddenly drops to zero
whenever the sample cooled below 4.2K.
 On measuring the resistance of a small tube filled with mercury, he
was astonished to observe that its resistance fell from ∼0.1 Ω at a
temperature of 4.3 K to less than 3 × 10−6 Ω at 4.1 K.
 So he conclude that super conductors are materials that can conduct
electricity or transport electrons from one atom to another atom with
no resistance.
 The temperature at which the mercury becomes superconducting is
known as its critical temperature Tc.
Super conductors :- The ability of certain metals and alloys exhibit
almost zero electrical resistivity when
temperature.
they are cooled to low
Graph showing the resistance of a specimen of mercury versus
absolute temperature.
Important parameter’s which define
super conducting state
Classification Of Superconductor Materials
Figure : variation of electrical resistivity with temperature
The Periodic Table showing all known elemental
superconductors and their critical temperatures.
Figure: critical magnetic field
Diamagnetic property (Meissener Effect)
London’s Equation
Contin…