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Superconductivity: The state of any conductor at which a conductor offers zero resistance is known as super conductivity and the material which shows superconductivity is known as superconductor.e.g. ceramic materials(Insulators at room temperature)
Resi
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Temperature0K 𝐓𝐜
Conductors
Superconductors
Breakdown of superconductivity
Superconductivity of a material has been breakdown if;1. Temperature is
increases2. Current density is
increases3. Magnetic field
increases
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J T
Meissner effect
Meissner effect is the phenomena of superconductors to opposing the magnetic field and vice versa.
Classification of Superconductors
These can be classified on base of:1. Magnetic field2. Critical Temperature3. Materials4. Operational Theory (BCS Theory)
1. Classification by Magnetic field
TYPE – I SN Transition abruptly occurs at
TYPE – IISN Transition gradually occurs between and
Where;S – SuperconductivityN – Normal StateSN – Mixed State of Superconductivity and Normal State
2. Classification by Critical Temperature
I – Low temperature superconductivity
The critical temperature range for low temperature super conductors is:
II – High temperature superconductivity
The critical temperature range for low temperature super conductors is:
3. Classification by Materials
Superconductor material classes include chemical elements (e.g. mercury or lead), alloys (such as niobium-titanium, germanium-niobium, and niobium nitride), ceramics (YBCO and magnesium diboride), or organic superconductors (fullerenes and carbon nanotubes).YBCO: Yttrium barium copper oxide
4. Operational Theory (BCS Theory)
According to BCS theory by Bardeen, Cooper and Schrieffer in 1957. In superconducting materials, below a certain critical temperature, an electron hitting an ion causes the lattice to vibrate like a bell. The vibration affects a nearby electron, causing it to be attracted to the first electron. The electrons bind together into so-called Cooper pairs, all of which share the same quantum state. This allows them to move as one, in a condensate, conducting current without resistance.
BY BCS Theory
1. The pairs of free electrons does couple through phonons are known as cooper pairs.
2. The energy of cooper pair is lower then the energy of two individual layers
3. The electrons in cooper pair have opposite spin so net spin of cooper pair is zero.
4. The electron is behave like bosons in super conductors.
Use of Superconductors
The superconductors are mainly used in:1. MRI(Magnetic Resonance Imaging) Scan:
2. Particle Accelerators.3. Maglev (The floating train).