Physics - Current Electricity Question with Solution | TestHub

The bridge formed with given resistances is a balanced Wheatstone's bridge The situation can be depicted as shown in the figure.As resistances $S$ and $6\Omega$ are in paralle, their effective resistance is $\frac{6S}{6+S}\Omega$. For balancing condition, $\frac{P}{Q}=\frac{R}{\left(\frac{6S}{6+S}\right)}$ or $\frac{2}{2}=\frac{2(6+\mathrm{S})}{6\mathrm{S}}$ or $3\mathrm{S}=6+\mathrm{S}\Rightarrow \mathrm{S}=3\Omega$