A potentiometer $$PQ$$ is set up to compare two resistances, as shown in the figure. The ammeter $$A$$ in the circuit reads 1.0 A when the two-way key $$K_3$$ is open. The balance point is at a length $$l_1$$ cm from $$P$$ when the two-way key $$K_3$$ is plugged in between 2 and 1, while the balance point is at a length $$l_2$$ cm from $$P$$ when the key $$K_3$$ is plugged in between 3 and 1. The ratio of two resistances $$\frac{R_1}{R_2}$$, is found to be: