In a potentiometer circuit, a cell of EMF 1.5 V gives balance point at 36 cm length of wire. If another cell of EMF 2.5 V replaces the first cell, then at what length of the wire, the balance point occurs?

(1) 60 cm

(2) 21.6 cm

(3) 64 cm

(4) 62 cm

*Solution*

We have, $\frac {E_1}{E_2}=\frac {l_1}{l_2}$

$\Rightarrow \frac {1.5}{2.5}=\frac {36}{l}$

$\Rightarrow l=60$ cm

Answer: (1)