Question

In potentiometer experiment when terminals of the cell is at distance of $52cm$, then no current flows through it. When $5\Omega$ shunt resistance is connected in it then balance length is at $40cm$. The internal resistance of the cell is

• A. $5$ $\Omega$
• B. $\frac{200}{52}$ $\Omega$
• C. $\frac{52}{8}$ $\Omega$
• D. $1.5$ $\Omega$

Answer 1

The correct option is D $1.5$ $\Omega$

Given,

$R=5\Omega$

$l_1=52cm,l_2=40cm$

To find,

Internal resistance of cell, $r=?$

$r=R(\frac{l_1}{l_2}-1)=5(\frac{52}{40}-1)=5\left(\frac{52-40}{40}\right)=5\left(\frac{12}{40}\right)=5\left(\frac{3}{10}\right)=\frac{15}{10}=1.5\Omega$

$\Rightarrow r=1.5\Omega$

Therefore, the internal resistance of the cell is $1.5\Omega$