Question

In a potentiometer experiment the galvanometer shows no deflection when a cell is connected across $60 \,cm$ of the potentiometer wire. If the cell is shunted by a resistance of $6 \,\Omega$ the balance is obtained across $50 \,cm$ of the wire. The internal resistance of the cell is

• A. $0.5\, \Omega $
• B. $0.6 \,\Omega $
• C. $1.2 \, \Omega $
• D. $1.5 \,\Omega $

Answer 1

Answer: (C)

For potentiometer, the internal resistance $r$, is given by
$r=\left(\frac{l_{1}}{l_{2}}-1\right) R$
Given, $l_{1}=600 \,cm$,
$l_{1}=50 \,cm $
$R=6\, \Omega$
$\therefore r=\left(\frac{60}{50}-1\right) 6=1.2\, \Omega$