Principle and Working:
Meissner effect, the expulsion of a magnetic field from the interior of a material that is in the process of becoming a superconductor, that is, losing its resistance to the flow of electrical currents when cooled below a certain temperature, called the transition temperature, usually close to absolute zero. The Meissner effect, a property of all superconductors, was discovered by the German physicists W. Meissner and R. Ochsenfeld in 1933.
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In the present setup, the transition temperature of high temperature superconductor BSCCO (Bismuth) is measured. A probe chamber with its attached thermocouple is used for liquid nitrogen in which the superconducting probe (sample) is cooled to below its critical temperature of approximately 93 K or -180 °C. The superconductivity probe so designed precisely is based on four- point measurement for resistivity, the end points of which are for fixed current and middle points for voltage drop. A temperature sensor is also attached on the surface of the sample. The voltage drop across the sample is measured as a function of the sample temperature using the voltage sensor.