Q: In a potentiometer experiment when a battery of e.m.f. 2 V is included in the secondary circuit, the balanced point is 500 cm. Find the balancing of the same end when a cadmium cell of e.m.f. 1.018 V is connected to the secondary circuit.
Sol. E ∝ ℓ
$\large \frac{E_1}{E_2} = \frac{l_1}{l_2} $
$\large l_2 = \frac{E_2}{E_1} \times l_1 $
$\large l_2 = \frac{1.018}{2} \times 500 $
= 254.5 cm.