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Superconductors

Nathan Finney

Michael Gammon

Newell Jensen



Superconductors

An element, inter-metallic alloy, or compound that will

conduct electricity without resistance below a certain

temperature, magnetic field, and applied current.

Definition of Superconductor:



efinitions !c" !his is the critical temperature at which the resisti#ity of a

superconductor goes to $ero. Abo#e this temperature the material is non-superconducting, while below it, the material becomes superconducting.

%c" !he scientific notation representing the &critical field& or ma'imum

magnetic field that a superconductor can endure before it is &(uenched& andreturns to a non-superconducting state. )sually a higher !c also brings ahigher %c. !ype ** superconductors ha#e lower %c+ and upper %c, critical

fields.



efinitions

Jc" !he scientific notation representing the &critical current density&

or ma'imum current that a superconductor can carry without becoming non-superconducti#e.

Meissner Effect: 'hibiting diamagnetic properties to the total

e'clusion of all magnetic fields. Named for /alter Meissner.0 !his isa classic hallmar1 of superconducti#ity and can actually be used tole#itate a strong rare-earth magnet.



Superconductor !ypes

!ype * 'hibits perfect diamagnetism below transition temperature !c and has only one

critical magnetic field %c.

!ype **!otally e'pels and e'cludes magnetic flu' below lower critical field %c+ and partially does so between %c+ and upper critical field %c,2 all superconductors e'cept

elements are !ype **. !his type has a larger !c than that of a !ype * superconductor.

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A %rief 3istory of Superconductors *n +4++ superconducti#ity was first obser#ed in mercury by utch physicist 3ei1e 5amerlingh 6nnes of 7eiden )ni#ersity. /hen he cooled it to the temperature of li(uid helium,

8 degrees 5el#in, its resistance suddenly disappeared9

*n +4:: /alter Meissner and ;obert 6chsenfeld disco#ered that a superconducting material will repel a magnetic field. !his phenomenon is 1nown as perfect diamagnetism and isoften referred to as the Meissner effect.

Since then ma<or de#elopments ha#e been made in both the disco#ery of higher temperature superconductors as well as progress in the theory of superconducti#ity. *n +4=> the +stma<or ad#ancement in the theory was made by American physicists John %ardeen, 7eon ?ooper, and John Schrieffer. !heir Theories of Superconductivity became 1nown as the%?S theory - abbre#iated for the first letter of each man@s last name - and won them a Nobel pri$e in +4>. %?S theory e'plained superconducti#ity at temperatures close toabsolute $ero for elements and simple alloys. 3owe#er, at higher temperatures and with different superconductor systems, the %?S theory has become inade(uate to fully e'plainhow superconducti#ity is occurring.



3istory continued

*n +4B %rian . Josephson, a graduate student at ?ambridge )ni#ersity, predicted

that electrical current would flow between superconducting materials - e#en whenthey are separated by a non-superconductor or insulator9 3is prediction thatsuperconductors would e'hibit this (uantum effect on a macro scale was laterconfirmed and won him a share of the +4>: Nobel Cri$e in Chysics. !his tunneling

phenomenon is today 1nown as the &Josephson effect& and has been applied toelectronic de#ices such as the SD)* Superconducting Duantum *nterferencee#ice0, an instrument capable of detecting e#en the wea1est magnetic fields.

More recently scientists ha#e made impro#ements in the area of predicting andengineering new types of superconductors. *n the Es carbon basedsuperconductors as well as ceramic superconductors were de#eloped. !hesesuperconductors ha#e fantastic magnetic properties as well as high criticaltemperatures, but their mechanical properties are poor.



Application of Superconductors

•Particle Accelerators

•Generators

•Transportation

•Power Transmission

•Electric Motors

•Military

•Computing

•Medical

•B Field Detection S!"#DS$

The Yamanashi MLX01 MagLev train



H%a?u:>

isco#ered" +4E> by Caul ?hu

!c" 4-4=5

%c," + !esla at >> 5

Jc" +.'+4

AIm,

at >> 5 ;eferred to as +--:K superconductor

because of the ratio of the three metallic

elements

!ype" !ype ** ?eramic



/or1s ?ited

http"IIimr.chem.binghamton.eduIlabsIsuperIsuperc.html,

7attice Cicture0, accessed 8I+8I=.

c1, Joe. http"IIsuperconductors.org, accessed :I=I= - 8II=.

Coole Jr., ?harles C., 3andboo1 of Superconducti#ity, ,

Academic Cress.

!horton L ;e', Modern Chysics for Scientists and ngineers nd ed.,

, !homson 7earning.

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