question_answer

In a potentiometer experiment, it is found that no current passes that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of \[\text{5 }\Omega \], a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.   [JEE Main Online 08-04-2018]

A) \[2\,\Omega \]

B) \[\text{2}\text{.5 }\Omega \]

C) \[\text{1 }\Omega \]

D) \[\text{1}\text{.5 }\Omega \]

Correct Answer: D

Solution :

[d]

\[\left( \frac{E}{r+5} \right)5=K\times 40\]

\[\Rightarrow 2r+10=13\]

\[\Rightarrow r=1.5\,\,\Omega \]