Question

In an experiment with potentiometer, 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 shift to $63 \,cm$. The emf of the second cell is

• A. 3.25 V
• B. 2.5 V
• C. 2.25 V
• D. 2 V

Answer 1

Answer: (C)

Given $l_{1}=35\, cm,\, l_{2}=63\, cm$
$E_{1} =1.25\, V ; E_{2}=?$
$\therefore \frac{E_{1}}{E_{2}} =\frac{l_{1}}{l_{2}}$
$E_{2} =\frac{l_{2}}{l_{1}} \times E_{1}$
$=\frac{63}{35} \times 1.25$
$=2.25\, V$