A Potentiometer wire of length $L$ and a resistance $r$ are connected in series with a battery of emf $E_0$ and a resistance $r_1$. An unknown emf E is balanced at a length $l$ of the potentiometer wire. The emf E will be:
Answer & explanation
Correct answer: option 3
$ I = \frac{E_0}{r+r_1}$
$ E = I \times \frac{l r}{L} = \frac{E_0 r}{r+r_1} \frac{l}{L}$