Current Electricity

In potentiometer experiment, the balancing length is \(8 \mathrm{~m}\) when two cells \(E_1\) and \(E_2\) are joined in series. When two cells are connected in opposition the balancing length is \(4 \mathrm{~m}\). The ratio of the e.m.f. of the two cells \(\left(\frac{E_1}{E_2}\right)\) is