User:Ela.agarkar

Superconductivity - Superconductivity is a phenomenon occurring at very low temperatures in many electric conductors in which the electrons responsible for conduction undergo collective transition to an ordered state with many unique and remarkable properties. These include the vanishing of resistance to the flow of current, the appearance of large diamagnetism and other unusual magnetic effects, substantial, and alteration of many thermal properties and the occurrence of quantum effects otherwise observable only at the atomic and subatomic level. It is found that for some materials resistivity suddenly drops to zero when cooled below certain temperature (known as Critical temperature)this zero resistivity property is termed as “Superconductivity”. It was first discovered in 1911 by the Dutch physicist, Heike Kamerlingh Ones. For certain materials like mercury,the resistivity suddenly drops to zero at very low temperature typically near the boiling point of liquid helium. This phenomenon is known as “Superconductivity”. This phenomenon is much different from conductivity as some of the best conductors like gold, silver, copper do not show superconductivity at any temperature whereas some ceramics which are insulators at room temperature shows superconductivity. For normal conductors resistance decreases with temperature and reaches a minimum value at T=00 K as shown in fig 5.1(Non-Superconductive Metal Graph), whereas for superconductors resistivity suddenly drops to zero below certain temperature as in fig 5.1(Superconductor graph) Superconductivity is a property of some conductors the resistivity of which suddenly drops to zero at certain low temperature, TC. These materials behaves as semiconductors below the critical temperature TC and as normal conductors above it as shown in fig,. 5.1 Therefore, superconductors are defined as the conductors with zero resistivity below a certain low temperature. The critical temperature (TC) is the transition temperature at which the normal state of a conductor changes to superconducting state.•	The critical temperature is different for different superconductors. For mercury TC is 4.2 K