Question

In a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35 cm length of the wire. If the cell is replaced by another cell, the balance point shifts to 63 cm, then emf of the second cell is

• A. 4.25 V
• B. 2.25 V
• C. 3.25 V
• D. 1.25 V

Answer 1

The correct option is B 2.25 V

$\text{Given :}{E}_1=1.25V,l_1=35cm,l_2=63cm$

$\text{Step 1:}$

The potential gradient of wire, $K=\frac{E}{l}$ will remain constant, Therefore EMF of external cell is proportional to the balance length

$\therefore \frac{E_1}{E_2}=\frac{l_1}{l_2}$ $....\left(1\right)$

$\text{Step 2: Substituting the values in equation (1)}$

So, $\frac{1.25}{E_2}=\frac{35}{63}$ or $E_2=2.25V$