# A potentiometer circuit has been set up for finding the internal resistance of given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of.(i).  Infinity(ii). 9.5 the 'balancing lengths', on the potentiometer wire are found to be 3 m and 2.85 m, respectively.The value of internal resistance of the cell is: Option 1) 0.25  Option 2) 0.95  Option 3) 0.5  Option 4) 0.75

$r=\left ( \frac{l_{1}-l_{2}}{l_{2}}\right )R$

$=\left ( \frac{3-2.85}{2.85}\right )\left ( 9.5 \right )$

$r=0.5\Omega$

Option 1)

0.25

This option is incorrect

Option 2)

0.95

This option is incorrect

Option 3)

0.5

This option is correct

Option 4)

0.75

This option is incorrect

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