1. the circuit diagram shows the use of a potentiometer to measure a small emf produced by a thermocouple connected between X and Y. The cell C, of emf 2 V, has negligible internal resistance. The potentiometer wire PQ is 1.00 m long and has resistance 5 Ω. The balance point S is found to be 400 mm from P. Calculate the value of emf V, generated by the thermo-couple.