Question

In a potentiometer experiment, the balancing with a cell is at a length of $240cm$. On shunting the cell with a resistance of $2\Omega$, the balancing length becomes $120cm$. The internal resistance of the cell is

• A. $1\Omega$
• B. $0.5\Omega$
• C. $4\Omega$
• D. $2\Omega$

Answer 1

The correct option is D

$2\Omega$

Step 1: Enlist the known values and formula

Given that, $R=2\Omega ,$and the balancing length $L_1=240cm$ and $L_2=120cm$.

The internal resistance $r$ of a cell is given as,

$r=R\left[\frac{L_1}{L_2}-1\right]$

Step 2: Calculate the internal resistance

Upon substituting the values we get,

$r=2\left[\frac{240}{120}-1\right]$

$=2\left(2-1\right)$

$=2\Omega$

Hence, the internal resistance of the cell is $2\Omega$.