A potentiometer circuit has been setup for finding. The internal resistance of a given cell. The main battery used a negligible internal resistance. The potentiometer wire itsefl is `4 m` long. When the resistance, `R`, connected across the given cell, has value of
(i) Infinity `9.5 Omega`,
(ii) the 'balancing length' , on the potentiometer wire are found to be `3 m` and `2.85 m`, respectively.
The value of internal resistance of the cell is

Options

A. `0.95 Omega`
B. `0.5 Omega`
C. `0.75 Omega`
D. `0.25 Omega`

Answer

B

Explanation

`r = ((l_1)/(l_2) -1) R = ((3)/(2.85) -1) xx 9.5 = (0.15)/(2.85) xx 9.5 = 0.5 Omega`.