A $6 \mathrm{V}$ battery of internal resistance $1 \mathrm{\Omega }$ is connected across a uniform wire $\mathrm{AB}$ of length $100 \mathrm{cm}$. The positive terminal of another battery of E.M.F $4 \mathrm{V}$ and internal resistance $1 \mathrm{\Omega }$ is joined to the point $\mathrm{A}$ as shown. The distance of point $\mathrm{P}$ from $\mathrm{A}$ is $\alpha \times 10 \mathrm{c}\mathrm{m}$. Find the value of $\alpha$, for which there is no current through the galvanometer. (resistance of $\mathrm{AB}$ wire is $5 \mathrm{\Omega }$)