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Satish Kumar Tiwari

Roll No-08119016050

EE 3rd Year

Under the Guidence of 

Mr. Chiranjit Sain

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 What is superconductivity?

Superconductivity in a material may bedefined as a phenomenon in which the

resistivity of material becomes zero.

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 History

Superconductivity was discovered in 1911 by Kamerlingh Onnes who noticed that the resistivity of Hg metal vanished abruptly at about 4K.

Meissner proposed the diamagnetic behavior of superconductors in 1933.

Macroscopic view of superconductivity Ginzburgand landau in 1950. 

The BCS model pointing the microscopic view of the superconductor in 1957 by Bardeen ,Cooper andSchrieffer. 

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  Behaviour of

Super conductors

1. Zero resistance

 2.Persistent currents 

Fig:1

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3. Perfect diamagnetism 

4. Energy gap 

Fig:2 Fig:3

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 Meissner Effect

  Walther Meissner and Robert Ochsenfeld discovered the phenomenon in1933 by measuring the magnetic field distribution outside superconducting tinand lead

The samples, in the presence of an applied magnetic field, were cooled belowtheir superconducting transition temperature.

It was seen that the sample became diamagnetic

They detected this effect only indirectly; because the magnetic f lux is conservedby a superconductor, when the interior field decreased the exterior fieldincreased.

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  Theories of superconductivity 1. Ginzburg-Landau theory (1950)

FS = FN + α |Ψ|2 +β/2|Ψ|4 

FS = Free Energy of Superconducting State

FN = Free Energy of Normal StateΨ = Complex order parameter 

2. The Microscopic BCS theory (1957)

Energy Gap, E=3.52KB TC √(1-T/TC )

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  Classification

By their physical properties

By the theory to explain them

By their critical temperature 

By material 

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Examples 

Magnesium diboride

Bismuth strontium calcium copperoxide

 Yttrium barium copper oxide

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Magnesium diboride (MgB2) :It has a critical

temperature of 39 K (−234 °C; −389 °F) and is the highestamongst conventional superconductors.

Fig:4

Fig:5

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PIT process

Manufacturing of superconducting wire/tapes

Fig:6

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  Applications

1. Sensitive magnetometers such as SQUIDS

Fig:7

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2.Powerful superconducting magnets are used inmaglev trains

Fig:1

Fig:8

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3.Used in NMRI & MRI machines

4.Used in Magnetic confinement

fusion reactors

5.Fast fault current limiter(used inpower transmission)

6.Rail Gun

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Future projects under actionTres amigas Project of America:

Fig:9

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Thus superconductors have proved beyondimagination because of its usefulness inadvancement of modern technological era.

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