A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. $E_0$ and a resistance $r_1$. An unknown e.m.f. E is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by :

Question

( A ) $\frac{E_0 L}{ \ell}$
( B ) $\frac{LE_0 r}{ \ell r_1}$
( C ) $\frac{LE_0 r}{( r + r_1 ) \ell}$
( D ) $\frac{E_0 r}{( r + r_1 )} \frac{\ell}{L}$