SUPER CONDUCTORS

SUPER- CONDUCTIVITY

Prof. K. Onnes in 1911, discovered that certain metals and alloys at low temperature (-265  to -170 ^oC) lost their resistance  considerably  .this phenomenon is known as superconductivity .

 As the temperature decreases, the resistance of material also decreases, but when the temperature reaches a certain critical value called transition temperature the resistance of the material completely disappears and it becomes zero.

 Then the material behaves as if is a super conductor and there will be flow of electrons without any resistance. The critical temperature for the different materials is different.

Generally the critical temperature for the mercury is -268.8 ^oC, and niobium at the critical temperature -263.7 ^oC since last 25 years LOTS OF RESEARCH is going on this topic scientists are trying to make such kind of alloys having high critical temp. Around -125 ^oC.

Examples of few alloy having the critical temperature -128 ^oC Bi₂Ca₂Sr₂Cu₃O₁₀ and Tl₂Ca₂Ba₂Cu₃O₁₀ at -148^oC.

The cause of super conductivity is that the free electrons in super conductor are no longer independent but some mutually dependent and coherent when the critical temperature is reached.

The ionic vibration which could deflect the free electron in metal is unable to deflect this coherent or cooperative cloud of electrons in super conductors. It means the coherent cloud of electrons makes no collision with ion of the super conductor and, as such there is no resistance offered by the super conductor to the flow of electrons.

Applications of super conductors

1.    Super Conductors are used to produce very high speed computers.

2.    Super conductors are used for the transmission of electric power

3.    Super Conductors are used in making strong electro magnets.