Question

The daniel cell is balanced on $125cm$ length of a potentiometer. Now, the cell is short circuited by a resistance of $2\Omega$ and the balance is obtained at $100cm$. The internal resistance of the daniel cell is :

• A. $\frac{4}{3}\Omega$
• B. $1.5\Omega$
• C. $1.25\Omega$
• D. $0.5\Omega$

Answer 1

The correct option is D $0.5\Omega$

Here, $r=R(\frac{I_1}{I_2}-1)=2(\frac{125}{100}-1)$
$=2(\frac{5}{4}-1)=2\times \frac{1}{4}=0.5\Omega$