Physics - Current Electricity Question with Solution | TestHub

Length of the potentiometer wire, $L=4\text{ m}=400\text{ cm}$

Potential difference across the wire, $V=3\text{ V}$

Potential gradient of the wire, $k=\frac{V}{L}=\frac{3}{400}\text{ V/cm}$

Balancing length for the cell, $l=100\text{ cm}$

The e.m.f. of the cell is given by $E=kl$

$E=\left(\frac{3}{400}\right)\times 100=\frac{3}{4}=0.75\text{ V}$

Answer: $0.75$ V