Question

A potentiometer wire is $10m$ long and a potential difference of $6V$ is maintained between its ends. The emf of a cell which balances against a length of $180cm$ of the potentiometer wire is:

• A. $1.8V$
• B. $1.1V$
• C. $1.08V$
• D. $1.2V$

Answer 1

Answer: (C)

$1.08V$

formula $\frac{E}{E_1}=\frac{l}{l_1}$
E - potential difference across ends $=6V$

$E_1$ - emf of cell
$l$ - length of wire
$l_1$ - balancing length
$\frac{6}{E_1}=\frac{1000}{180}$

$E_1=\frac{108}{100}$
$E_1=1.08V$