The current through a resistor in a circuit is 0.6 A. On putting a resistance of 2 Ω in parallel with the resistor, the current drops to 0.9 A. The resistance of the resistor is

1.0 Ω

The correct answer is Option (1) → 1.0 Ω

$I_1 = 0.6 \ \text{A}, \quad I_2 = 0.9 \ \text{A}$

$R = ?$

$\text{Let emf } = V$

$V = I_1 R = 0.6R$

$R_{\text{parallel}} = \frac{2R}{R + 2}$

$V = I_2 \cdot R_{\text{parallel}}$

$0.6R = 0.9 \cdot \frac{2R}{R+2}$

$0.6R(R+2) = 1.8R$

$0.6R^2 + 1.2R = 1.8R$

$0.6R^2 - 0.6R = 0$

$0.6R(R - 1) = 0$

$R = 1 \ \Omega$

The resistance is $1 \ \Omega$.