Question

In potentiometer experiment a cell of emf. 1.5 V. connected in the secondary circuit gives a balancing length of 165cm of the wire. If a resistance of 5$\Omega$ is connected parallel to the cell, the balancing length of the wire is 150cm. The internal resistance of the cell is

• A. 5$\Omega$
• B. 1.5$\Omega$
• C. 1$\Omega$
• D. 0.5$\Omega$

Answer 1

The correct option is D 0.5$\Omega$

In potentiometeric circuit we know that,

$\Rightarrow r=R(\frac{l_1}{l_2}-1)$
hence putting all the values we get
$r=5(\frac{165}{150}-1)=0.5\Omega$