24-03-2012, 05:48 PM
i jst need a ppt of super conducting generator wch i need for my technical presentation
24-03-2012, 05:48 PM
i jst need a ppt of super conducting generator wch i need for my technical presentation
20-09-2012, 05:17 PM
SUPERCONDUCTING MATERIALS
superconducting-materials.ppt (Size: 690.5 KB / Downloads: 119) Transition Temperature or Critical Temperature (TC) Temperature at which a normal conductor loses its resistivity and becomes a superconductor. Definite for a material Superconducting transition reversible Very good electrical conductors not superconductors eg. Cu, Ag, Au Types Low TC superconductors High TC superconductors Magnetic Flux Quantisation Magnetic flux enclosed in a superconducting ring = integral multiples of fluxon Φ = nh/2e = n Φ0 (Φ0 = 2x10-15Wb) Effect of Pressure Pressure ↑, TC ↑ High TC superconductors – High pressure Thermal Properties Entropy & Specific heat ↓ at TC Disappearance of thermo electric effect at TC Thermal conductivity ↓ at TC – Type I superconductors MEISSNER EFFECT When the superconducting material is placed in a magnetic field under the condition when T≤TC and H ≤ HC, the flux lines are excluded from the material. Material exhibits perfect diamagnetism or flux exclusion. Deciding property χ = I/H = -1 Reversible (flux lines penetrate when T ↑ from TC) Conditions for a material to be a superconductor Resistivity ρ = 0 Magnetic Induction B = 0 when in an uniform magnetic field Simultaneous existence of conditions Applications Large distance power transmission (ρ = 0) Switching device (easy destruction of superconductivity) Sensitive electrical equipment (small V variation large constant current) Memory / Storage element (persistent current) Highly efficient small sized electrical generator and transformer SUPERCONDUCTORS Superconductivity is a phenomenon in certain materials at extremely low temperatures ,characterized by exactly zero electrical resistance and exclusion of the interior magnetic field (i.e. the Meissner effect) This phenomenon is nothing but losing the resistivity absolutely when cooled to sufficient low temperatures WHY WAS IT FORMED ? Before the discovery of the superconductors it was thought that the electrical resistance of a conductor becomes zero only at absolute zero But it was found that in some materials electrical resistance becomes zero when cooled to very low temperatures These materials are nothing but the SUPER CONDUTORS. WHO FOUND IT? Superconductivity was discovered in 1911 by Heike Kammerlingh Onnes , who studied the resistance of solid mercury at cryogenic temperatures using the recently discovered liquid helium as ‘refrigerant’. At the temperature of 4.2 K , he observed that the resistance abruptly disappears. For this discovery he got the NOBEL PRIZE in PHYSICS in 1913. In 1913 lead was found to super conduct at 7K. In 1941 niobium nitride was found to super conduct at 16K Cryotron The cryotron is a switch that operates using superconductivity. The cryotron works on the principle that magnetic fields destroy superconductivity. The cryotron is a piece of tantalum wrapped with a coil of niobium placed in a liquid helium bath. When the current flows through the tantalum wire it is superconducting, but when a current flows through the niobium a magnetic field is produced. This destroys the superconductivity which makes the current slow down or stop.
05-10-2012, 12:07 PM
to get information about the topic "superconducting generators" full report ppt and related topic refer the link bellow
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