### JEE Mains Previous Years Questions with Solutions

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### AIEEE 2005

In a potentiometer experiment the balancing with a cell is at length $240$ $cm.$ On shunting the cell with a resistance of $2\Omega ,$ the balancing length becomes $120$ $cm$. The internal resistance of the cell is
A
$0.5\Omega$
B
$1\Omega$
C
$2\Omega$
D
$4\Omega$

## Explanation

The internal resistance of the cell,

$r = \left( {{{{\ell _1} - {\ell _2}} \over {{\ell _2}}}} \right) \times R$

$= {{240 - 120} \over {120}} \times 2 = 2\Omega$