A potentiometer wire is $4 \mathrm{~m}$ long and potential difference of $3 \mathrm{~V}$ is maintained…
A potentiometer wire is $4 \mathrm{~m}$ long and potential difference of $3 \mathrm{~V}$ is maintained between the ends. The e.m.f. of the cell which balances against a length of $100 \mathrm{~cm}$ of the potentiometer wire is
$0.50\mathrm{V}$
$0.60 \mathrm{~V}$
$0 .75 \mathrm{~V}$
$0 .25 \mathrm{~V}$
Solution
Potential gradient $=\frac{3}{4} \frac{\mathrm{V}}{\mathrm{m}}$
So, emf against $100 \mathrm{~cm}=\frac{3}{4} \times 1 \mathrm{~V}=0.75 \mathrm{~V}$