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 \( \text{mA} \)) through the resistor \( R_1 \) is ________.
