TOPIC : SUPERCONDUCTIVITY ROLL NOS. : 21 TO 26

PRESENTED BY1.VARUN2.YASH G.3.SARVESH4.MADHURA5.NIKITA 6.SIDDHANT

Superconductivity

Exploring the world of Low Temperatures and Quantum effects

Introduction

What are superconductors?• Superconductors are the material having almost zero

resistivity and behave as diamagnetic below the superconducting transiting temperature

• Superconductivity is the flow of electric current without resistance in certain metals, alloys, and ceramics at temperatures near absolute zero, and in some cases at temperatures hundreds of degrees above absolute zero = -273ºK.

Discoverer of Superconductivity Superconductivity was first discovered in

1911 by the Dutch physicist,Heike Kammerlingh Onnes.

The Discovery Onnes, felt that a cold wire's resistance would

dissipate. This suggested that there would be a steady decrease in electrical resistance, allowing for better conduction of electricity.

At some very low temperature point, scientists felt that there would be a leveling off as the resistance reached some ill-defined minimum value allowing the current to flow with little or no resistance.

Onnes passed a current through a very pure mercury wire and measured its resistance as he steadily lowered the temperature. Much to his surprise there was no resistance at 4.2K.

Superconducting magnetsAn electrical current in a wire creates a magnetic field around a wire. The strength of the magnetic field increases as the current in a wire increases. Because SCs are able to carry large currents without loss of energy, they are well suited for making strong magnets. When a SC is cooled below its Tc and a magnetic field is increased around it, the magnetic field remains around the SC. If the magnetic field is increased to a critical value Hc the SC will turn normal.

• Support a very high current density with a very small resistance• A magnet can be operated for days or even months at nearly constant field

A typical Nb3Sn SC magnet.It produces 10.8T with a current of 146A. Bore diameter is 3.8 cm.

Cross-section of multifilamentNb-Ti of 1mm overall diameter,consisting from 13255 5-mfilaments

Other Uses of Superconductivity

Fault current limiters• Electric motors

• Electric generators• Petaflop computers (thousand

trillion floating point operations per second)

A superconductor like this, called a Type I superconductor, is limited in its current-carrying capability because it can tolerate only very small

magnetic fields.

The Meissner effect is the litmus test for superconductivity.

A Type II superconductor acts like a Type I superconductor in small magnetic fields. In large magnetic fields, it “sacrifices” part of itself so

that the rest can remain superconducting.

Type II superconductors can carry enormous currents and make incredibly powerful superconducting electromagnets.

Picture below is the levitation of a magnet above a cooled superconductor, the Meissner Effect

High-Tc Superconductivity

Alex Müller and Georg Bednorz

Paul Chu

K.A. Muller J. G. Bednorz

The Discovery of superconductivity in ceramic materials

The Nobel Prize in Physics 1987

Super conductor

lattice

Super conductor lattice

Due to attract of electron by positive charge, ions in conductor

is disturbed

Ions attracted by positive charges

Due to deformation positive charge

increased

Electrons get attracted due to increased positive

charges

Cooper pairs formed

advantages Can carry large quantities of energy

without heat loss.

Able to generate strong magnetic fields.

Superconductors beneficial applications in medical imaging techniques.

New superconductive films may result in miniaturization .

Superconductors increased speed in computer chips.

disadvantage

Superconducting materials conduct current at only given temperature known as transition temperature.

Superconductors still do not show up in most everyday electronics.

MAGNETIC LEVITATION Magnetic levitation, maglev,

or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational and any other accelerations.

The two primary issues involved in magnetic levitation are lifting force: providing an upward force sufficient to counteract gravity, and stability: insuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized.

APPLICATIONS Magnetically levitated vehicles are called Maglev vehicles

Maglev trains: Based on two techniques:

1)Electromagnetic suspension 2)Electrodynamic suspension

In EMS,the electromagnets installed on the train bogies attract the iron rails. The magnets wrap around the iron & the attractive upward force is lift the train.

In EDS levitation is achieved by creating a repulsive force between the train and guide ways.

The basic idea of this is to levitate it with magnetic fields so that there is no physical contact between the trains and guideways. Consequently the maglev train can travel at hihg speed of 500 km/h.

Maglev Train

2. The production of sensitive magnetometers based on SQUIDs.

Powerful superconducting electromagnets used in maglev trains, Magnetic Resonance Imaging (MRI) and Nuclear magnetic resonance (NMR) machines, magnetic confinement fusion reactors

(e.g. tokomaks), and the beam-steering and focusing magnets used in particle accelerators.

• Superconducting generators has the benefit of small size and low energy consumption than the conventional generators.

• Very fast and accurate computers can be constructed using superconductors and the power consumption is also very low.

Superconductors can be used to transmit electrical power over very long distances without any power or any voltage drop

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