Question

A cell, shunted by a 8 Ω resistance, is balanced across a potentiometer wire of length 3 m. The balancing length is 2 m when the cell is shunted by 4 Ω resistance. The value of internal resistance of the cell will be _____ Ω.

Answer 1

$\frac {ε_18}{r_1+8}3c$

$\frac {ε_14}{r_1+4}2c$

$⇒ \frac {2(r_1+4)}{r_1+8}=\frac 32$
Then, the value of internal resistance of the cell,
$⇒ r_1 = 8 Ω$

So, the answer is $8 Ω$.