If `K_2` is open balancing length is 600cm, if `K_2` is closed 350cm is balancing length. Calculate the internal resistance.

A potentiometer wire of length 100 cm has resis tance of 10 ohms. It is connected in series with a resistance R and a cell of emf 2V and negligible in ternal resistance. The circuit is as shown below. -If a source of emf 10 milli volts is balanced by a length of 40cm of the potentiometer wire, find the value of the external resisatnce

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery used across the potentiometer wire, has an emf of 2V and negligible internal resistance. The potentiometer itself is 4m long. When the resistance 'R_(1)' , connected across the given cell has values of (i) infinity (ii) 9.5Omega , the balancing length on the potentiometer wire are found to be 3m and 2.85m respectively. The value of internal resistance of the cell is