In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf 1.5 V is found to be 60 cm. If this cell is…

In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf $\displaystyle 1.5$ V is found to be $\displaystyle 60$ cm . If this cell is replaced by another cell of emf E, the length-of null point increases by $\displaystyle 40$ cm . The value of $\displaystyle E$ is $\displaystyle \frac{x}{10} V$. The value of $\displaystyle x$ is $\displaystyle \_\_\_\_$.