Question

In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf $15 \,V$ is found to be $60 \,cm$ If this cell is replaced by another cell of emf $E$, the length-of null point increases by $40 \,cm$ The value of $E$ is $\frac{x}{10} V$ The value of $x$ is _______

Answer 1

The correct answer is 25.
E2​E1​​=l2​l1​​
E2​1.5​=60+4060​=106​=53​
E2​=25​=10x​
x=25