Question

A daniel cell is balanced on 125 cm length of a potentiometer wire. When the cell is short circuited with a $2\Omega$ resistance, the balancing length obtained is 100 cm. Internal resistance of the cell will be

• A. $1.5\Omega$
• B. $0.5\Omega$
• C. $1.25\Omega$
• D. $\frac{4}{5}\Omega$

Answer 1

The correct option is B $0.5\Omega$

By using $r=\frac{l_1-l_2}{l_2}\times R^{{}^{\prime }}\Rightarrow r=\frac{125-100}{100}\times 2=\frac{1}{2}=0.5\Omega$