Question

In a potentiometer experiment, experimental cell used in secondary circuit is balanced against $240cm$ length of potentiometer wire. On shunting this experimental cell with a resistance of $2\Omega ,$ the balancing length becomes $120cm.$ The internal resistance of the cell is

• A. $4\Omega$
• B. $2\Omega$
• C. $1\Omega$
• D. $0.5\Omega$

Answer 1

The correct option is B $2\Omega$

According to potentiometer experiment:

The internal resistance of the cell is defined as:

$r=R(\frac{l_1}{l_2}-1)$

putting values:

$r=2(\frac{240}{120}-1)=2\Omega$