The resistance of superconductor has to be measured at different temperatures. This resistance, being very low, requires 4-wore measurement technique to eliminate lead resistance. Four electrical contacts were made in a line on the surface of the specimen. The current was passed through the two outer connections and voltages measured at two inner points of contact. The voltage measurement was taken for two opposite directions of current and then averaged so as to cancel any thermal effects the temperature was measured by chromel-alumel thermocouple. The sample, in a pallet form was mounted on a Cu sheet and in thermal contact with it. One end of thermocouple was attached to the Cu sheet. The sample assembly was kept in a glass tube which in turn was cooled in a Dewar flask. Dewar flask was half filled with liq. N2 so that a thermal gradient sets up in the space above liquid nitrogen. The temperature of the sample was varied by changing the position of it in this space.
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