A potentiometer is an accurate and versatile device to make elechical measurements of E.M.F. because the method involves :

Question

$\begin{array}{1 1} (1) cells\\ (2) potential \;gradients \\ (3) \text{ a condition of no currenl flow through the galvanometer} \\ (4) \text{a combination of cells, galvanometer and resistances} \end{array} $