1) The denial cell is balanced on the 125 cm length of a potentiometer. Now, the cell is short-circuited by the resistance of $2 \Omega$ and the balance is obtained at 100 cm . The internal resistance of the denial cell is A) $\frac{4}{3}\Omega$ B) $1.5 \Omega$ C) $1.25 \Omega$ D) $0.5 \Omega$ Answer: Option DExplanation:Here, $r=R\left(\frac{I_{1}}{I_{2}}-1\right)=2\left(\frac{125}{100}-1\right)$ $=2\left(\frac{5}{4}-1\right)=2\times\frac{1}{4}=0.05 \Omega$
