By :

Tanvi JainAditi Gupta

HEIKE . K . ONNES

He was the first Scientist who studied about SUPERCONDUCTIVITY.

Mercury (Tc = 4.2 K)

Helium (B.P = 4.2K)

Extremely Surprising Result :

RRESISTANCEESISTANCE == == 00

The following table shows the Critical Temperature of various Superconductors :-

MATERIAL TYPE CRITICALTEMPERATURE (K)

ZINC METAL 0.88 k

ALUMINIUM METAL 1.19 k

TIN METAL 3.72 k

CREAMICS PEROVSKITES 37 K

YTTRIUM BARIUM COPPER OXIDE

ALLOY 92 K

NIOBIUM METAL 9.2 K

MAGNESIUM I BOURIDE

ALLOY 138 K

MERCURY BARIUM CALCIUM COPPER OXIDE

ALLOY I64 K ( Under 30 G Pa of Pressure )

LEAD METAL 7.2 K

YTTRIUM BARIUM COPPER OXIDE

Theories Explaining Superconductivity :

During 1950sGinzburg & Landau Theory

{ Mathematical }Barden Cooper Scieffer (BCS) Theory

{ Microscopic }

GINZBURG & LANDAU THEORY :

Without Magnetic Field :

Below Superconducting Transition Temperature :                          

Bardeen Cooper Schrieffer Theory

The electrons pair to the fermi level (10^-15 m)

This is known an PHONON interaction..

What actually happens at Low Temperature ?

Region of vibration

ElectronLets go

Critical Temp. Reached…

Now lets understand the cooper interaction…

This part becomes +vely charged….

And ….

Understanding Cooper Pair Interaction…

The Cooper Interaction (BCS theory)

PROPERTIES OF SUPERCONDUCTIVITY

No Power Loss :

Electrons can travel through them freely.

They can carry large amounts of electrical current for long periods of time without losing energy as heat.

Meissner Effect :

Perfect dimagnetism.

Has implications for making high speed, magnetically-levitated trains.

The classic demonstration of the MEISSNER EFFECT.

MAGLEV TRAIN

MAGLEV

Use copper coils in the track which use repulsion to lift the train up to make it levitate.

Superconducting magnets on the train.

TRACK MAGNETS – Accelerate and brake

MAGNETIC RESONANCE IMAGING (MRI) :

MRI OUTPUT (BRAIN)

NUCLEAR MAGNETIC RESONANCE (NMR) :

ABOUT NMR :

Drug discovery, biotechnology & materials science.

Homogeneous & Strong Magnets in NMR spectroscopy.

MAGNETOMETER :

LOGIC : SENSING VERY SMALL MAGNETIC FIELDS.

Used to detect Submarines.

Measure the magnetic field produced by your brain.

To find ore deep deposited underground.

Sense minute signals from stars etc.