The galvanometer deflection, when key K₁ is closed but K₂ is open, equal ${\theta }_0$(see figure). On closing K₂ also and adjusting $R_2$ to $5\Omega$, the deflection in galvanometer becomes $\frac{{\theta }_0}{5}$ . The resistance of the galvanometer is, then given by [Neglect the internal resistance of battery]