A potentiometer wire of length 100 cm and resistance \(3\,\Omega\) is connected in series with resistance of \(8\,\Omega\) and an accumulator of 4 volt whose internal resistance is \(1\,\Omega\).
A cell of e.m.f. \(E\) is balanced at 50 cm length of the wire. The e.m.f. of the cell is