Answer –
According to the question statement –
Internal resistance of the cell is r = 1.5 V cell
Balance point of the cell in open circuit is l = 76.3 cm
External resistance is R = 9.5 Ω
New balance point is l1 = 64. 8 cm
Then, the expression for internal resistance is given by the relation –
\[r=R\left[ \frac{l}{{{l}_{1}}}-1 \right]r=9.5\left[ \frac{76.3}{64.8}-1 \right]\]
\[r=1.69\Omega \]