In a potentiometer experiment, the balancing length for a cell $240 \mathrm{~cm}$. On shunting the cell with…
In a potentiometer experiment, the balancing length for a cell $240 \mathrm{~cm}$. On shunting the cell with a resistance of $2 \Omega$, the balancing length become half the initial balancing length. The internal resistance of the cell is
$1.5 \Omega$
$1 \Omega$
$0.5 \Omega$
$2 \Omega$
Solution
The internal resistance is given by
$\begin{aligned}
& r=R\left(\frac{\ell_1-\ell_2}{\ell_2}\right) \\
& =2\left(\frac{240-120}{120}\right)=2 \Omega
\end{aligned}$