As shown in the figure, the resistance of a galvanometer $$G$$ can be found by the half-deflection method. Here the resistance $$R_2$$ is adjusted such that when the key $$K$$ is closed the deflection in the galvanometer becomes half of the value as compared to when $$K$$ is open. Half-deflection is obtained at $$R_2=4\,\Omega$$ and thus the galvanometer resistance is found to be $$6\,\Omega$$. In this half-deflection condition the current (in mA) through the resistor $$R_1$$ is: