Question

A potentiometer has uniform potential gradient across it. Two cells connected in series (i) to support each other and (ii) to oppose each other are balanced over 6 m and 2 m respectively on the potentiometer wire. The emf’s of the cells are in the ratio of

• A. 1 : 2
• B. 1 : 1
• C. 3 : 1
• D. 2 : 1

Answer 1

The correct option is D 2 : 1

If suppose emf’s of the cells are $E_1$ and $E_2$ respectively then
$E_1+E_2=x\times 6$ .........(i) [x = potential gradient) ]
and $E_1-E_2=x\times 2$ ........(ii)
$\Rightarrow \frac{E_1+E_2}{E_1-E_2}=\frac{3}{1}\Rightarrow \frac{E_1}{E_2}=\frac{2}{1}$