In a meter bridge, the wire of length 1 m has a non-uniform cross-section such that, the variation dR/(d l) of its resistance R with length l is…

In a meter bridge, the wire of length $\displaystyle 1$ m has a non-uniform cross-section such that, the variation $\displaystyle \frac{\mathrm{dR}}{\mathrm{d} l}$ of its resistance R with length $\displaystyle l$ is $\displaystyle \frac{\mathrm{dR}}{\mathrm{d} l} \propto \frac{1}{\sqrt{l}}$. Two equal resistances are connected as shown in the figure. The galvanometer has zero deflection when the jockey is at point P. What is the length AP ?